B P7 C65 Supraventricular Tachycardia Flashcards
1
Q
SVT is an umbrella term used to describe tachycardias (atrial and/or ventricular rates in excess of _____ bpm at rest), the mechanism of which involves tissue from the His bundle or above.
A
> 100 bpm
2
Q
For example, some patients may simply develop a subjective awareness of their heartbeat, which is often described as a slow forceful beating. Frequently these symptoms will be most obvious at _____ and will often be reported while lying on the _____ side presumably as the cardiac apex is felt more clearly against the chest wall.
A
Night
Left-hand side
3
Q
Symptoms of ectopic beats are most usually reported as a skipped beat associated with a strange sensation in the _____.
A
Throat or an impulse to cough
4
Q
Symptomatic sinus tachycardia produces regular palpitations with heart rate generally in the range of _____ bpm, although it can be much faster depending on the underlying cause
A
120 to 130 bpm
5
Q
SVT is usually described as _____
A
Sudden in onset with rapid racing (often too fast to count) with a sensation that the heart is trying to beat out of the chest.
May be triggered by sudden movements such as sudden running for the bus or by bending and standing up.
May last continuously from minutes to hours and terminate suddenly. They may respond to vagal maneuvers.
6
Q
Recurrent short bursts (seconds to minutes) of rapid palpitations with normal rhythm interspersed suggests an automatic _____.
A
Focal AT
7
Q
Prolonged irregularly irregular racing points to _____.
A
Atrial fibrillation (AF)
8
Q
Sudden syncope is rarely associated with SVT and when arrhythmic in origin generally suggests _____.
A
Ventricular tachycardia (VT)
Significant pause of sinus arrest
AV block
9
Q
Routine blood tests include _____. When patients present to an emergency department with tachyarrhythmias, _____ will often be elevated. In this setting, this is a nonspecific response frequently secondary to the tachycardia and not necessarily indicative of obstructive coronary artery disease
A
Biochemistry and thyroid function tests
Troponin
10
Q
Most important is documentation of the _____.This may involve finding ambulance traces or emergency department ECGs
A
Tachycardia
11
Q
For patients without documented arrhythmias, a range of monitoring strategies are available and may be chosen according to symptom frequency and patient preference. When symptoms occur daily, simple _____ will obtain the diagnosis.
A
24-hour Holter monitoring
12
Q
Documentation of onset and termination of the arrhythmia may add important diagnostic information. For example, an _____ may have gradual increase in rate over 30 seconds to several minutes, whereas a _____ usually has sudden onset with a “warm-up” over several beats.
A
IAST: 30s to mins
Focal AT: “warm-up” over several beats
13
Q
Finally, in patients with classic symptoms of sudden onset and offset tachycardia highly suggestive of SVT, documentation is not essential and an initial approach of a diagnostic _____ may be considered.
A
Electrophysiologic study (EPS) with a view to catheter ablation
14
Q
__________________ clinical syndrome characterized by the presence of a regular and rapid tachycardia of abrupt onset and termination.
A
Paroxysmal SVT
15
Q
Unusual symptom of SVTs
A
Syncope
16
Q
_______________ may be reported during and early after SVT episodes due to release of atrial natriuretic peptide at these elevated rates
A
Polyuria
17
Q
_______________ very common in the general population. In an unselected population over the age of 50, the average frequency was approximately 1 or 2 per hour and increased with each decade of life. 3 Increase in atrial ectopy occurred not only in relation to advancing age but also in association with other cardiovascular disease.
A
Atrial Premature Complexes or Ectopic Beats
18
Q
Atrial premature complexes are very common in the general population. In an unselected population over the age of 50, the average frequency was approximately _____ per hour and increased with each decade of life
A
1 or 2 per hour per dacade
19
Q
Transient increase in atrial ectopics may occur in response to _____.
A
Intercurrent illness
Stress and anxiety
Response to alcohol and caffeine
20
Q
Although in the vast majority of patients atrial premature complexes are benign, the seminal paper by Haissaguerre et al. described the triggering of AF by focal atrial ectopics originating from sleeves of myocardium within the _____.
A
Pulmonary veins
21
Q
Longitudinal studies have described an association between excess PACs (>___/hour or runs of nonsustained AT >___ beats) and the outcomes of incident AF, stroke, and death.
A
> 30/hour or runs of nonsustained AT >20 beats
22
Q
In 15-year follow-up, patients with excess PACS and a CHADs-VASc score of ___ or greater demonstrated an annual stroke risk comparable to that of patients with AF
A
2
23
Q
A number of opinions have suggested that atrial ectopy and AF may be markers of an underlying atrial myopathy that is the primary determinant of stroke risk and adverse outcomes. Isolated case reports have indicated that frequent PACs (_____% daily burden) also may be associated with development of a reversible cardiomyopathy.
A
20% to 40%
24
Q
Despite the association of frequent atrial ectopy with potential for adverse events, to date there is no evidence that treatment of isolated atrial ectopy reduces risk or improves long-term outcomes. Therefore, the only indication for treatment of PACs is when they are sufficiently_____. The vast majority of patients with atrial ectopics will not require any treatment other than _____. n those with severe symptoms, treatment would initially involve a _____.
A
Symptomatic
Reassurance
Beta blocker or calcium channel antagonist
25
In highly symptomatic patients unresponsive to or intolerant of medication, catheter ablation may be considered when the _____.
Ectopic burden is high and the atrial ectopic is unifocal in origin
26
The appearance of an atrial ectopic on an ECG is characterized by an _____.
Early atrial beat with a P wave morphology different from that of the sinus beat
27
An atrial ectopic may be conducted normally, with _____ but also may be nonconducted
Prolongation of the PR interval and possibly aberrancy or widening of the QRS
28
A _____ is one of the most common causes of an unexpected pause on an ECG
Nonconducted or blocked atrial ectopic
29
_____ AT has been defined as atrial activation starting rhythmically at a small area (focus) from which it spreads out centrifugally. Impulses occur with a given periodicity separated by a quiescent interval recorded on the surface ECG as an isoelectric period
Focal AT
30
In _____, activation occurs around a large central obstacle, such as an anatomic structure or region of scarring; electrical activity can be recorded throughout the entire atrial cycle length.These include _____ and other well-characterized macroreentrant circuits in the right and left atrium, which are also frequently referred to as types of “atypical AFL.”
Macroreentry
Typical AFL
31
More recently a third category of AT has been described although not routinely included in all classifications.These have been termed _____
“Small circuit” or “localized” reentry
32
Focal AT is a form of SVT characterized by _____.
Regular, organized atrial activity with discrete P waves and typically an isoelectric segment between P waves
33
Mechanisms of focal AT include _____.
(1) Abnormal or enhanced automaticity (abnormal impulse initiation in an individual or cluster of myocytes)
(2) Triggered activity (abnormal impulse initiation due to oscillations of membrane potential, termed early or delayed after-depolarizations)
(3) Reentry (when myocardial regions activated later in propagation reexcite regions that have already recovered excitability)
34
Focal AT is the least common mechanism of PSVT, accounting for approximately _____% of patients with PSVT.
10% to 20%
35
Focal AT is usually manifested by atrial rates between _____ bpm but may be as low as 100 bpm or as high as 300 bpm
130 and 250 bpm
36
It should be noted that brief (_____ beats) nonsustained AT is a common finding on routine Holter recordings and is seldom associated with symptoms
3 to 10 beats
37
AT usually demonstrates an _____. In contrast, IAST _____.
In addition, demonstration that onset occurs with a tightly coupled P wave, particularly located in the preceding T wave, is virtually diagnostic of AT
AT: abrupt onset and termination or may warm up and cool down over 3 or 4 beats
IAST: gradually increases in rate over approximately 30 seconds to several minutes
38
The most important differentiating factor on ECG between AT and AVNRT and AVRT is the _____ relationship.
Both typical AVNRT and AVRT have a _____ R-P interval that does not vary (the former superimposed on the QRS and the latter in the ST segment), and the P wave morphology usually cannot be clearly discerned.
R-P relationship
AVNRT/AVRT: Short RP interval
AVNRT: superimposed on QRS
AVRT: superimposed on ST segment
39
Although most commonly associated with a _____ R-P interval, AT can occur with either a short R-P interval or a long R-P interval depending on the tachyardia rate and the speed of AV nodal conduction. It can therefore mimic either AVNRT or AVRT.
The ability to demonstrate ____ of the R to P relationship invariably indicates AT.
Long RP interval
RP: “unlinking” or variability
40
Another clue to the diagnosis of AT is the presence of an _____ P wave axis. This excludes AVRT or AVNRT because it suggests an origin high in the atrium. A superiorly directed P wave vector may indicate _____.
Inferior P wave: AT
Superior P wave: AVRT or AVNRT or an AT focus originating from the coronary sinus ostium or annular structures.
41
The rate range of **focal AT** is usually between ____ bpm but may be as low as 100 bpm or as high as 300 bpm.
Similarly, although **macroreentrant atrial arrhythmias** usually have a rate between _____ bpm, conduction delays within the circuit either due to atrial pathology or use of conduction slowing antiarrhythmics can slow the rate to less than 150 bpm
Focal AT: 130 and 250 bpm
Macroreentrant AT: 240 and 310 bpm
42
Focal ATs do not occur randomly throughout the atria but rather have a characteristic anatomic distribution. In the right atrium they tend to cluster around the _____. In
the left atrium, the majority
originate from the _____.
Right: 75%
Crista terminalis - 31%
Coronary sinus ostium (CS os) - 8%
Para-Hisian or perinodal region - 11%
Tricuspid annulus (TA) - 22%
RA appendage
Left:
Pulmonary veins - MC (Ostium of PV) - 19%
Mitral annulus - MC (Supperior MA) - 4%
LA appendage
Left septum being less common
43
In general, an upright P wave in V1 suggests __ origin whereas a negative P wave in V1 suggests __ origin.
Upright P in V1: LA
Negative P in V1: RA
44
_____ is clinically defined as a tachycardia that can be induced and terminated with programmed stimulation and has a P wave morphology identical or similar to that of the sinus P wave
Sinus node reentry
45
Initial management of a focal AT in the emergency department might involve administration of _____ as for other mechanisms of SVT (_____ mg intravenously). For focal AT, the arrhythmia may either _____.
Adenosine 6-12 mg IV
Response:
* Terminate
* Transiently slow, and then return to the pre-adenosine rate
* Continue with AV block and unmasked P waves
46
It is now well recognized that the sinus node is not a discrete structure but rather a diffuse pacemaker complex located along the long axis of the _____.
Crista terminalis
47
Catheter ablation is recommended as a first-line therapy in patients with _____ focal AT as an alternative to pharmacologic therapy (class 1)
Symptomatic
85% success rate
48
If adenosine is unsuccessful, _____ may be effective in hemodynamically stable patients. If ineffective, antiarrhythmic agents such as _____ may be considered. Alternatively, if drug treatment is unsuccessful or the patient is hemodynamically unstable, _____ may be used. This would be inappropriate for automatic forms of tachycardia with recurrent bursts of tachycardia separated by 1 or more sinus beats
Intravenous beta blockers or calcium channel blockers (verapamil or diltiazem)
Flecainide, ibutilide, or amiodarone
Synchronized DC cardioversion
49
IAST is defined as an _____. The mean 24-hour heart rate is above _____ bpm.
Elevated heart rate of greater than 100 bpm at rest or on minimal exertion out of keeping with the level of activity or stress
>90 bpm
49
When drug therapy for focal AT is preferred, _____ may be considered. In patients without structural or ischemic heart disease, _____ also may be considered.
Beta blockers or non-dihydropyridine calcium channel blockers (verapamil or diltiazem)
Propafenone or flecainide
50
The heart rate in IAST is not necessarily persistently elevated, and considerable fluctuation is often present. Resting heart rates are frequently in the _____ range, and diurnal variation is generally preserved. However, significant rate increases occur with ______ and at other times may be unexplained
Normal
Minor activity and positional changes
51
Heart rate in IAST increases generally occur _____ in contrast to onset of **focal AT**, which demonstrates _____ and perhaps “warm-up” phenomenon over 2 to 3 beats.
IAST:
Gradually over 30 seconds to several minutes
Focal AT;
Sudden onset with a tightly coupled initiating beat
52
The P wave morphology of IAST reflects an origin in the region of the _____ in the right atrium with a biphasic positive-negative appearance in V1 and upright P waves in inferior leads and lead I
Superior crista terminalis
53
Treatment of IAST
(1) **Effective communication, support, and reassurance**, which may improve outcomes
(2) Lifestyle interventions such as **exercise training and volume expansion** may be helpful
(3) **Ivabradine**, a selective blocker of the pacemaker current (If) has been found to be safe and effective in several small trials.
(4) Addition of **beta blockade to ivabradine therapy** or the use of **beta blockers** alone may also be useful
54
AFL often occurs in the context of _____.
**Structural heart disease** (e.g., valvular, ischemic heart disease, cardiomyopathy)
** Acute disease process** (e.g., sepsis, myocardial infarction).
55
AFL and AF have been described as two sides of the same coin. The two arrhythmias frequently coexist clinically with documented AF in up to ___% of AFL patients.
75%
56
Antiarrhythmic agents such as _____, which slow atrial conduction, promote the conversion of AF to AFL
Class 1C:
Flecainide
Propafenone
Class III: Amiodarone
57
The risk of developing AF late after a flutter ablation is high and increases with both intensity of monitoring and duration of follow-up. In some studies the likelihood of detecting AF during 2 years of follow-up reaches 50%. Risk factors for developing AF after ablation of AFL include _____.
Previously documented AF
Impaired LV function
Ischemic and other structural heart disease
LA enlargement
58
In the setting of ___ flutter, patients may experience presyncope or syncope. In addition, in the presence of persistent rapid ventricular response rates of 2:1 flutter, patients may develop a decline in LV ejection fraction due to development of a TCM. This is usually fully reversible within approximately ____ months of resumption of sinus rhythm.
1:1 - Presyncope/syncope
2:1 - decline in LV fraction due to TCM
3 months
59
It can be considered to be a broad activation wavefront rotating between the tricuspid annulus (TA) anteriorly and the crista terminalis-eustachian ridge/infeior vena cava (IVC) posteriorly
CTI Dependent Flutter
60
In typical AFL, the ___ is the narrowest anatomic segment of the circuit. In the most common form (approximately 90%) the circuit rotates in a _____ direction when viewed in the frontal plane. In 10%, rotation is _____.
CTI
90% Counterclockwise
10% Clockwise
61
The ECG of typical counterclockwise AFL is characterized by the _____ demonstrating an initial gradual downsloping segment followed by a deeply inverted component with a terminal positive component. In the precordial leads, V1 classically demonstrates an initial isoelectric component followed by an upright component. With progression across the precordial leads, the initial component becomes inverted and the second component isoelectric such that V5 and V6 demonstrate an inverted flutter wave. Lead I is low amplitude/isoelectric and aVL usually upright
Classic inferior lead flutter wave appearance (“saw-tooth” pattern)
62
It has long been recognized that typical flutter has a characteristic rate of _____ bpm. With 2:1 conduction, this equates to a ventricular rate of _____ bpm
300 bpm
150 bpm
63
_____ are associated with slower flutter rates.
Marked RA enlargement
Atrial remodeling with significant conduction slowing
Antiarrhythmic agents which slow atrial conduction
64
In clockwise AFL, although the anatomic boundaries are identical to those of counterclockwise AFL, the wavefront is reversed and there is more variability in the ECG appearance. Nevertheless, characteristic features appear in the inferior leads where a _____ is preceded by an inverted segment. V1 is characterized by a broad negative and usually notched deflection with transition to an upright deflection in V6
Broad and notched upright component
65
Atypical flutter may occur primarily in the right or the left atrium. When the V1 flutter wave is deeply _____, this is highly likely to represent a right atrial circuit. Conversely, when the V1 flutter wave is upright, this generally indicates an LA circuit.
Inverted V1: RA circuit
Upright V1: LA circuit
66
AFL is classically described as showing a _____ of the flutter wave on the 12-lead ECG, reflecting continuous atrial activation. This distinguishes macroreentry from focal AT, which typically demonstrates _____.
Continuously undulating appearance (AFL)
Discrete P waves separated by an isoelectric interval (Focal AT)
67
Conversely, when focal AT is very rapid (e.g., >___ bpm), the P waves may appear to show continuous undulation.
>250 bpm
68
The pathology underlying atypical flutter is highly variable, and these circuits may occur in the context of :
(1) prior corrective atrial surgery (congenital heart disease [CHD], valvular heart disease, after a Maze procedure or cardiac transplantation)
(2) previous AF ablation
(3) advanced atrial disease associated with atrial enlargement (these patients frequently have underlying pathologies such as heart failure [systolic or diastolic] or unoperated valvular heart disease such as severe mitral regurgitation)
(4) in patients with normal atrial size and without an obvious underlying pathologic condition.
68
As noted earlier, a third category of AT termed ____ reentry has been increasing recognized in the era of high- density three-dimensional mapping. These reentrant circuits occur in a localized region with a diameter of 1 to 2 cm; the hallmark is that the _____.
Small circuit reentry
Entire circuit can be recorded on a single catheter with a high density of electrodes in this specific region
69
For patients with AFL who are hemodynamically unstable, ______ is indicated. For hemodynamically stable patients, _____ is also preferred if trained personnel are available. Alternatively, intravenous _____ may be trialed. These should be administered in hospital with careful monitoring for the potential risk of _____. This risk is increased in patients with impaired LV function.
Unstable: Synchronized cardioversion
Stable: DC cardioversion
Alternative: Ibutilide or oral dofetilide
Risk: ventricular proarrhythmia
70
For patients with AFL with implanted dual-chamber devices (pacemaker or defibrillator) attempts at _____ may be considered if appropriate expertise is available
High-rate atrial overdrive pacing
71
Rate control of ALF with _____ may be used for rate control.
Oral or intravenous beta blockers or non-dihydropyridine calcium channel blockers (verapamil or diltiazem)
72
_____ agents should not be used in patients with AFL because of the risk of slowing atrial rate and facilitating 1:1 AV conduction with concomitant profound conduction slowing in the ventricle
Class 1C
73
_____ now represents the cornerstone management strategy in patients with AFL. It may be considered after a first episode or in patients with recurrent or persistent episodes. It is particularly indicated in patients who develop TMC.
Catheter ablation
74
A common form of atypical flutter in the era of AF ablation is due to _____. These may occur in up to 20% of patients and are more common in those who have undergone persistent AF ablation, particularly when extensive or linear ablation has been performed or in those with more advanced atrial remodeling.
Circuits occurring after AF ablation procedures
75
In CTI-dependent flutter, ablation is across the CTI from the annulus to the eustachian ridge at the anterior margin of the IVC. The end point is the demonstration of _____ across this line using standard electrophysiology mapping techniques. The acute success rate is in excess of 97%, and the recurrence rate is now approximately 5% to 10%. The procedural risk of serious adverse events is under 1%
Bidirectional conduction block
76
For patients in whom catheter ablation for AFL is contraindicated (e.g., advanced age, comorbidities, patient preference) or is not feasible (e.g., presence of mechanical valves, multiple unstable circuits, previously failed) a number of antiarrhythmic agents may be considered for maintenance of sinus rhythm. These include _____ depending on efficacy, tolerability, and nature of comorbidities (e.g., amiodarone preferred in the presence of significant LV dysfunction).
Sotalol
Amiodarone
Dofetilide
77
For patients with AFL in whom a rhythm control strategy is unsuccessful or not preferred, a rate control strategy may be adopted. This might be with a ______. If drug therapy is unsuccessful or poorly tolerated and ventricular response rates remain high, ______ may be considered.
Beta blocker or a non- dihydropyridine calcium channel blocker (verapamil or diltiazem)
Pacing (usually biventricular or His bundle pacing) followed by AV node ablation
78
SVT is most classically a regular narrow-complex tachycardia with a wide rate range from just in excess of _____ bpm in some patients
100-250 bpm
79
In some patients with SVT, bundle branch aberrancy may be present during tachycardia. This is more commonly right bundle aberrancy due to the _____.
Longer refractory period of the right bundle compared with the left bundle
80
PSVT may be viewed as a subset of SVT and involves a classic clinical picture characterized by sudden onset and termination of rapid palpitations documented as a regular narrow-complex tachycardia.This clinical picture implies the presence of _____.
AVNRT
AVRT
AT (less frequently)
81
Polyuria is occasionally described as a feature of SVT and is presumed to be the result of ______.
Atrial natriuretic peptide release at rapid rates
81
Episodes of PSVT are usually initiated by _____. Patients frequently describe classic triggers such as _____, although a wide range of triggers with variable frequency have been reported
Atrial or ventricular ectopic beats or couplets
Sudden movements, bending over, or exercise
82
A description of multiple stop-start episodes in succession usually indicates a _____, whereas a single prolonged episode is more common with _____.
Focal AT - multiple stop-start
AVRT or AVNRT - single prolonged episode
83
Adults with a long history of episodes that began in childhood and teenage years are more likely to have _____ rather than AT.
AVNRT or AVRT
84
_____ is the most common documented mechanism of PSVT in patients undergoing catheter ablation
AV node reentry (AVNRT)
85
_____ is the most common mechanism of SVT in the first decade of life, accounting for 55% to 60% of PSVT cases.
AVRT
86
The AVNRT circuit most probably involves the _____.
Compact AV node
Perinodal transitional inputs to the node - left or right sided (fast and slow pathways)
Perinodal atrial region
87
The critical components of the AVNRT circuit are located within the anatomic triangle of Koch bounded _____. At the apex of the triangle is the compact node.
Anteriorly: TA
Posteriorly: tendon of Todaro
Superiorly: Membranous septum and the penetrating bundle of His
Inferiorly: Ostium of the coronary sinus
APSI - TaToMsHOc
88
The fast AV nodal pathway approaches the compact node at the _____, and the slow pathway approaches the node from the _____.
Fast: superior aspect of the triangle
Slow: inferior aspect of the triangle and the CS os region
Fast-UP
Slow-LOW
89
Regular narrow complex tachycardia with A > V
Focal AT
Arial flutter
AVNRT with block
90
Regular narrow complex tachycardia with A < V
JET
Fascicular VT
Concealed nodofascicular AP (very rare)
AVNRT with block to A
91
Regular narrow complex tachycardia with long RP (RP > PR)
Sinus tachycardia
Focal AT
Atypical AVNRT
Slowly conducting AP (PJRT)
92
Regular narrow complex tachycardia with short RP (RP < PR) with RP < 70ms (P wave within QRS):
Typical AVNRT
Focal AT
JET
93
Regular narrow complex tachycardia with short RP (RP < PR) with RP > 70ms (P wave within T wave):
Atypical AVNRT
AVNRT
Focal AT
94
In approximately 50% of cases of AVNRT, the P wave is not visible because it is occurs completely within the _____.
QRS
95
In 45% of cases of AVNRT, the final component of the P wave occurs at the tail end of the QRS, producing a _____.
V1: pseudo right bundle appearance
Inferior leads: pseudo S wave pattern
96
In approximately 50% of cases, the P wave is not visible because it is occurs completely within the QRS. In 45% of cases, the final component of the P wave occurs at the tail end of the QRS, producing a pseudo right bundle appearance in V1 and a pseudo S wave pattern in the inferior leads. This appearance has been reported to indicate typical AVNRT with an accuracy of _____%
100%
97
When onset of the tachycardia is recorded, an early atrial ectopic that blocks in the fast pathway (due to the relatively longer refractory period of the fast pathway) conducts down the slow pathway with a long PR interval is highly suggestive of _____. Activity then travels retrogradely via the fast pathway, which has now recovered excitability, and the tachycardia is initiated.
AVNRT
98
When cycle length variability occurs during the tachycardia, the presence of a fixed ventriculoatrial (VA) relationship (reflecting fast pathway conduction) provides strong evidence in favor of _____ rather than AT, in which this relationship is incidental
AVNRT
99
When termination of the tachycardia is documented, spontaneous termination with a _____ wave as the final event also provides strong evidence against AT and therefore in favor of AVNRT.
P wave: AVNRT
100
For acute AVNRT management, patients should be educated in vagal maneuvers to be performed in the supine position with leg elevation. When performed under instruction in the emergency department this may be effective in _____% of patients.
40-50%
101
In patients who fail vagal maneuvers for AVNRT, _____ is the treatment of choice. Care must be taken to warn the patient that they may feel chest tightness and a transient sense of impending doom.
Adenosine 6 to 12 mg IV bolus
102
In patients who fail adenosine reversion, _____ may be considered.
____ is appropriate in hemodynamically unstable patients or when all other measures fail but is rarely required.
IV verapamil or diltiazem
Alternatively: IV beta blocker (metoprolol or esmolol)
DC cardioversion
103
Patients with infrequent episodes of AVNRT associated with mild symptoms and that are responsive to vagal maneuvers may elect _____.
No treatment
104
However, for more frequent episodes, unpredictable episodes, or episodes with severe symptoms, the treatment of choice is _____.
Catheter ablation targeting the slow pathway region
105
Large series have confirmed the efficacy and safety of catheter ablation for both typical and atypical forms of AVNRT. Long-term success rates in excess of 95% are generally reported. In addition, large contemporary series have reported an incidence of AV block between _____% and no mortality.
0.1% and 0.4%
106
In patients with AVNRT who prefer medical therapy, the first-line long-term treatment options are either a _____. These may reduce the III frequency and duration of events but rarely abolish the tachycardia.
Non-dihydropyridine calcium channel blocker (verapamil or diltiazem) or a beta blocker
107
Clinical contexts where JET occurs
(1) Early after surgical CHD repair - 1-5%
(2) Congenital arrhythmia presenting in the 1st 6mo of life
(3) Pediatrics beyond 6mo
108
The prevalence of a Wolff-Parkinson-White (WPW) pattern on a sinus rhythm ECG in the general population has been estimated at between _____%
0.15% and 0.25%
109
Although not classically considered to be an inher- ited disorder, the prevalence does increase significantly among first- degree relatives of patients with WPW to _____%
0.55%
110
Accessory pathways may occur in the context of the _____ gene variant cardiac glycogenosis, which causes a syndrome characterized by cardiomyopathy with increased ventricular wall thickness, conduction disease and AV block, and ventricular preexcitation.
PRKAG2 gene
111
Accessory pathways are classically recognized in patients with _____, occurring in approximately 25% of this population. They occur in relation to the tricuspid valve malformation and are therefore invariably right sided; frequently there may be multiple path- ways, the majority of which are manifest
Ebstein anomaly
112
An _____ represents a congenital persistence of bridging AV working myocardium in the form of a muscle bundle.
Accessory pathway
113
Anatomically, accessory pathways are most commonly located along the _____ (60%); approximately 25% are in the _____, and a minority (15%) are on the _____.
60% - MA and termed left free wall pathways
25% - Septal region of the TA or MA
15% - Rght free wall
114
An accessory pathway may conduct in the _____ direction (termed manifest due to the characteristic ECG appearance), the retrograde direction, or both. When an accessory pathway conducts only in the _____ direction it is termed concealed and the surface ECG is normal. On occasion, manifest accessory pathways conduct in the antegrade direction only (these represent only approximately 10% of all accessory pathways).
Antegrade: Manifest
Retrograde: Concealed, normal surface ECG
115
The sinus rhythm 12-lead ECG of WPW classically exhibits a _____.
(1) Short PR interval (rapid conduction over the accessory pathway) (2) Slurred QRS onset (delta wave)
116
The QRS complex in WPW represents a _____.
Fusion beat between conduction over the accessory pathway and conduction over the AV node
117
_____ refers to the fact that conduction in the AV node slows further for an abnormally fast input such as an AT or AF
Decrement
118
In contrast, an _____ generally has rapid antegrade conduction such that there is a very short PR interval and the P wave is followed immediately by the QRS without an isoelectric interval.
Accessory pathway
119
Because initial ventricular activation occurs via the accessory pathway inserting directly into ventricular myocardium, the initial appearance of the QRS is a _____. However, shortly after this onset, activation over the AV node is complete and the remainder of ventricular activation then occurs rapidly over the His-Purkinje fibers
Slurred onset and the beginnings of a wide QRS (due to relatively slow ventricular conduction)
120
Preexcited atrial fibrillation, the hallmark of which is an _____.
Irregularly irregular wide-complex tachycardia that appears largely monomorphic (some variability may occur due to capture and fusion
121
A variety of ECG algorithms to predict the likely anatomic location of the accessory pathway are based on the delta wave vector. Broadly, a positive delta wave in V1 indicates a _____ -sided accessory pathway, a negative delta wave in V1 with early precordial transition to upright in V2 usually indicates a _____ accessory pathway , and later transition of the precordial delta wave at or after V3 most usually a _____ accessory pathway.
V1:
Positive: Left side accessory
Negative:
Early precordial transition to upright in V2: R septal accessory
Late transition at or after V3: R free wall
***Inferior leads:
Negative: Posterior
Positive: Anterior
122
The most common form of tachycardia associated with an accessory pathway is _____.
Orthodromic AVRT
***In patients with a manifest pathway, this accounts for 90% to 95% of AVRT episodes. This circuit involves antegrade conduction over the AV node and His-Purkinje system and is therefore classically a regular narrow-complex tachycardia.
123
Antidromic AVRT is a regular wide-complex arrhythmia in which antegrade conduction occurs over the ______, with retrograde activation occurring over the AV node or over a second accessory pathway present in 30% to 60% of patients with spontaneous antidromic AVRT
Accessory pathway (fully preexcited)
124
The development of AF in the presence of an accessory pathway with a short antegrade refractory period (<250 msec) and a shortest R-R interval during AF of less than 250 msec can result in ventricular response rates of up to 300 bpm with the potential to trigger _____.
Ventricular fibrillation (VF) and sudden death
125
In preexcited tachycardia, the arrhythmia originates in the atrium and is conducted passively to the ventricle over the _____, which acts as a bystander.
Accessory pathway
126
As with any regular narrow-complex SVT, initial management of AVRT may include _____.
In patients who fail vagal maneuvers, ____ is the treatment of choice but must be used with caution in AVRT due to the potential for induction of AF with rapid antegrade conduction over the accessory pathway.
Vagal maneuvers best performed in the supine position with leg elevation
Adenosine 6- to 12-mg intravenous bolus
126
The characteristic ECG in preexcited tachycardia is a _____.
Wide-complex tachycardia (maximal preexcitation) with an irregularly irregular ventricular rhythm
127
Acute treatment of preexcited AF when the patient is hemodynamically unstable is _____. When hemodynamically stable, drugs acting on the accessory pathway such as _____ may be used. _____ should be avoided because enhanced AV nodal conduction and VF have been described in a number of reports.
Unstable: DC cardioversion
Stable: Ibutilide, procainamide, or a class 1C agent (flecainide or propafenone)
Amiodarone
128
_____ is the treatment of choice for patients with symptoms associated with recurrent AVRT or who have sustained preexcited AF
Catheter ablation
129
_____ should be considered for concealed accessory pathway AVRT (no preexcitation on sinus rhythm ECG) when ablation is not preferred or is unsuccessful
Beta blockers or non-dihydropyridine calcium channel blockers (verapamil or diltiazem)
130
_____ may be considered for AVRT with a manifest or concealed accessory pathway when ablation is not preferred or has been unsuccessful and when no other contraindications are present (ischemic heart disease,impaired LV function etc.).
Class 1C agents (propafenone or flecainide)
131
Of patients with asymptomatic WPW, __% will go through life without arrhythmic events. In the __% who do develop arrhythmias, the most common is _____ in 80%%. Preexcited AF may develop in 20% to 30%, with the small associated risk of sudden death estimated at 2.4 per 100 person-years in patients with asymptomatic WPW.
No arrhythmias: 80%
Develop arrhythmias: 20% (MC: AVRT 80%)
132
Nevertheless, the 2019 European Society of Cardiology guidelines provide a Class 1 recommendation of catheter ablation in asymptomatic patients who have an accessory pathway with _____.
High-risk properties at EPS
133
Low-risk features of WPW include _____.
Intermittent loss of pre-excitation on ECG, Holter monitoring, or exercise stress test.
134
High-risk features of WPW include the _____.
(1) Presence of multiple accessory pathways
(2) Short antegrade refractory period of the accessory pathway
(3) Young age(the risk of sudden cardiac death associated with WPW is highest in the first two decades of life)
(4) Symptomatic AVRT episodes
135
Supraventricular arrhythmias are particularly common in adults late after repair of CHD. The most common mechanism is _____ due to circuits around scars and prosthetic material. They are most common in patients with more complex forms of CHD such as _____.
Macroreentrant AT (atypical flutter)
Fontan repair for single ventricular physiology or Mustard or Senning repair for D-TGA
136
Differentials in patients with regular wide-complex tachycardia
Ventricular tachycardia
Fascicular tachycardia
SVT with bundle branch aberrancy
-Rate-related
-Preexisting
-Antiarrhythmic induced (e.g., flecainide)
-Metabolic derangement (e.g., hyperkalemia)
Accessory pathway related
-Antidromic tachycardia
-Preexcited tachycardia (atrial tachycardia or AVNRT with bystander
accessory pathway)
Rapid ventricular pacing
137
A range of different stepwise, points-based, and single criteria methods have been devised that largely are focused on the same key criteria. These have included
(1) the AV relationship and specifically whether AV dissociation is present
(2) morphologic QRS criteria asking the question of whether this is a typical left or right bundle branch block pattern;
(3) QRS duration (broader in VT)
(4) activation velocity of the initial and terminal components of the QRS (initial RS interval shorter in SVT with aberrancy)
(5) chest lead concordance, with negative or positive being highly specific for VT but relatively insensitive
(6) QRS axis (e.g., northwest axis rarely seen in SVT with aberrancy)
(7) when available, com- parison with the baseline ECG may provide important clues
(8) onsets, terminations, and transitions may provide diagnostic information. For example, transition from wide to narrow complex or the reverse at a similar rate is highly suggestive of SVT with aberrancy; and
(9) beyond the ECG alone, the clinical con- text can provide critically import- ant information
