B P7 C65 Supraventricular Tachycardia Flashcards
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.
> 100 bpm
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.
Night
Left-hand side
Symptoms of ectopic beats are most usually reported as a skipped beat associated with a strange sensation in the _____.
Throat or an impulse to cough
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
120 to 130 bpm
SVT is usually described as _____
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.
Recurrent short bursts (seconds to minutes) of rapid palpitations with normal rhythm interspersed suggests an automatic _____.
Focal AT
Prolonged irregularly irregular racing points to _____.
Atrial fibrillation (AF)
Sudden syncope is rarely associated with SVT and when arrhythmic in origin generally suggests _____.
Ventricular tachycardia (VT)
Significant pause of sinus arrest
AV block
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
Biochemistry and thyroid function tests
Troponin
Most important is documentation of the _____.This may involve finding ambulance traces or emergency department ECGs
Tachycardia
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.
24-hour Holter monitoring
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.
IAST: 30s to mins
Focal AT: “warm-up” over several beats
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.
Electrophysiologic study (EPS) with a view to catheter ablation
__________________ clinical syndrome characterized by the presence of a regular and rapid tachycardia of abrupt onset and termination.
Paroxysmal SVT
Unusual symptom of SVTs
Syncope
_______________ may be reported during and early after SVT episodes due to release of atrial natriuretic peptide at these elevated rates
Polyuria
_______________ 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.
Atrial Premature Complexes or Ectopic Beats
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
1 or 2 per hour per dacade
Transient increase in atrial ectopics may occur in response to _____.
Intercurrent illness
Stress and anxiety
Response to alcohol and caffeine
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 _____.
Pulmonary veins
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.
> 30/hour or runs of nonsustained AT >20 beats
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
2
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.
20% to 40%
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 _____.
Symptomatic
Reassurance
Beta blocker or calcium channel antagonist
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
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
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
A _____ is one of the most common causes of an unexpected pause on an ECG
Nonconducted or blocked atrial ectopic
_____ 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
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
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
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
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)
Focal AT is the least common mechanism of PSVT, accounting for approximately _____% of patients with PSVT.
10% to 20%
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
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
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
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
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
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.
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
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
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
_____ 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
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
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
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
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
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
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
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
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
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
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
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).
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%
