Chou's Flashcards
Progressive shortening of the PR interval with
corresponding widening of the QRS complex,
and vice versa, without change in the duration
of the P-end QRS interval is called
Concertina effect
The WPW ECG pattern with full preexciation
contains the following elements:
- A PR interval of less than 0.12 second,
with a normal P wave - Abnormally wide QRS complex with
a duration of 0.11 second or more - The presence of initial slurring of the QRS
complex, the delta wave - Secondary ST segment and T wave changes
A normal “septal” q wave is seldom found in
the preexcited complexes. Its presence in lead
__ is believed to exclude preexcitation.
V6
The WPW pattern occurs more often in males/females?
males
most important clinical manifestations in patients with WPW syndrome
Paroxysmal tachycardias
Paroxysmal supraventricular tachycardia is responsible for 75 to 80 percent of all paroxysmal tachycardias in patients with WPW syndrome.
Diagnostic criteria on the surface ECG and in the intracardiac electrogram during tachycardia include the following for orthodromic reentry tachycardia
(1) the P wave is negative in lead I
(2) PR is longer than RP when the retrograde pathway is fast (most common pattern) and shorter than RP when the retrograde pathway is slow
(3) the P wave is inscribed after, not during, the QRS complex; and
(4) the tachycardia cycle length is prolonged in the presence of functional ipsilateral bundle branch block (BBB).
(5) is an occasional occurrence of electrical alternans during tachycardia.
(6) is the sequence of the atrial excitation. The earliest excitation of the impulse conducted retrogradely via the AV node takes
place near the atrial septum
(7) the demonstration that the
impulse is conducted from the ventricle to the
atria at the time when the His bundle is refractory.
The effect of drugs is criterion (8). The effective
refractory period of the AV node and of the
AP is lengthened by different categories of drugs
(i.e., adenosine, b-adrenergic blockers, calcium
channel blockers, and digitalis for the AV node
and class 1A sodium channel blockers for the
AP). Therefore the response to a drug may be
helpful occasionally in the differential diagnosis
between AV node reentrant and AV reentrant
tachycardia
In some cases of AV reentrant tachycardia, the AP conducts the impulse as slowly as or slower than the normally conducting AV node. Such decremental conduction was found in 7.6 percent of APs in 653 patients.
Most of these atypical APs are located in the posteroseptal region and the associated tachycardia is called the ____________, as was first described by Coumel et al
permanent form of junctional reciprocating tachycardia
The tachycardia tends to be “incessant.” It is usually initiated by lengthening of the PR interval or a premature complex and can be produced or aggravated by antiarrhythmia drugs
Coumel and Attueldescribed a phenomenon called the _________ ” They showed that if BBB was present during tachycardia, a premature impulse elicited in the ventricle of the blocked bundle branch could be followed by a VA interval shorter than the VA interval of the tachycardia complexes because there is no delay caused by conduction around the blocked bundle branch.
“paradoxical capture.
The anterograde effective refractory period is the longest A1A2 interval recorded nearest the AP at which A2 conducts to ventricles without preexcitation.
the longest V1V2 interval recorded nearest the AP with the activation sequence compatible with retrograde conduction through the accessory bypass tract.
retrograde effective refractory period
An accessory AV pathway may be capable only of retrograde conduction. Anterograde block in the AP with preserved retrograde conduction results in an absence of the WPW pattern on the surface ECG (i.e., concealment of the bypass tract). This is AKA
The pathway is called concealed accessory pathway or bypass
However, the bypass tract can be utilized in the retrograde direction as a link in the AV reentrant circuit
When a reentrant tachycardia occurs in association with such a concealed bypass, the condition is called concealed WPW syndrome. It is the most common variant form of WPW syndrome and occurs in about 20 to 30 percent of patients with APs
findings during tachycardia to be suggestive of a concealed bypass tract
(1) negative P wave in lead I (because of left-sided bypass and early left atrial depolarization), (2) P wave during the ST segment, and
(3) increased cycle length if functional left bundle branch block (LBBB) develops
Conditions favorable for development of antidromic tachycardia include:
(1) short, effective refractory period of the entire retrograde VA conduction system
(2) short anterograde effective refractory period of the AP; and
(3) location of the bypass tract farther from the AV node
even if the term remains in use, it should not be applied to the ECG findings of short PR interval and normal QRS, with no history of paroxysmal tachycardia.
In 1941 Mahaim andWinston97 described muscular bridges connecting the AV node and ventricular myocardium, as well as discrete connections between the fascicles to the ventricles. Almost all Mahaim fibers are ____ sided (right or left?)
right
right atriofascicular fibers crossing the tricuspid annulus serve as the basis for typical Mahaim conduction in most if not all of these patients
In the absence of reentrant tachycardia, Mahaim fibers can be suspected when two different morphologies of the ventricular complex appear within a short time interval without any inter vening clinical events
Nodofascicular tachycardia should be suspected if:
(1) intermittent anterograde preexcitation is recorded
(2) the tachycardia can be initiated with a single atrial premature stimulus producing two ventricular complexes; and
(3) a single ventricular extrastimulus initiates supraventricular tachycardia without a retrograde His deflection
Drugs that can shorten effective refractory period of accessory pathways
Digitalis
beta blockers
CCB eg verapamil and diltiazem
Drugs that can prolong effective refractory period of accessory pathways
refractoriness is prolonged by class IA and class III antiarrhythmia drugs.
In most cases TDP is preceded by a sequence of a long RR interval of the dominant cycle followed by a short extrasystolic interval with premature depolarization interrupting the T wave AKA ____ phenomenon
(R-on-T phenomenon)
Kay and associates6 reported that such a sequence was seen during 41 of the 44 episodes of TDP that occurred in 32 patients. Such a sequence is not pathognomonic for TDP, however, as Gomes et al.7 also noted it frequently preceding ventricular tachycardia and ventricular fibrillation.
The risk is increased with increasing QTc duration and in the presence of
(1) hypokalemia, potassium deficiency, and perhaps hypomagnesemia
(2) impaired ventricular function
(3) severe bradycardia and second- or third-degree AV block
(4) T wave alternans; and
(5) R-on-T phenomenon.
Female gender is also a relative risk factor, as
in most series there is female preponderance of
this arrhythmia (ratio of female:male is about
3:1).
The clinical conditions known to predispose
to TDP are as follows:
1. Congenital long QT syndrome
2. Poisoningwith organophosphorus compounds.
3. Intracranial hemorrhage and complications
of air encephalography
4. Treatment with antiarrhythmic drugs.
5. Metabolic disturbances. TDP associated with significant QT prolongation has been reported in patients with hypothyroidism or anorexia nervosa and during treatment with “liquid protein” diets, other fad weightreducing diets, and therapeutic starvation.
6. Concomitant use of drugs that compete for or
inhibit the hepatic cytochrome P-450 3A4
7. Other drugs. Case reports of TDP associated
with QT lengthening incriminate a variety
of drugs. A partial list includes thioridazine,
amantadine, vincamine, ketanserin, astemizole,
pentamidine, trimethoprim-sulfamethoxazole,
vasopressin, and a mixture of Chinese medical herbs.
8. Transient QT prolongation often occurs
during the acute phase of (MI).
9. Other conditions. TDP has been reported in
several other conditions associated with
QT lengthening (e.g., after ionic contrast
injections into the coronary artery62) and
in patients with pheochromocytoma.
Many experimental studies suggest that TDP is initiated by a process known as ________ , which may also contribute to maintenance of the arrhythmia.
early afterdepolarizations
term applied to sudden death resulting from nonpenetrating chest wall impact in the absence of injury to the ribs, sternum, and heart, thereby differing from cardiac contusion.
commotio cordis
A regular tachycardia with a rate of 120 to 200 beats/min and a QRS duration of 0.12 second or longer may represent one of the following rhythms:
- Ventricular tachycardia
- Aberrant ve ntricular conduction
- Preexisting left (LBBB) or right (RBBB) bundle branch block
- Preexisting nonspecific intraventricular conduction defect
- Anterograde conduction through the bypass tract in patients with the Wolff-Parkinson- White (WPW) syndrome
- Anterograde conduction over an atriofascicular
or nodoventricular connection
An irregular wide QRS complex tachycardia may represent one of the following rhythms:
- Atrial fibrillation with aberrant ventricular conduction, bundle branch block, or intraventricular conduction defect.
- Atrial fibrillation with ventricular preexcitation. In the presence of a short refractory period of the bypass tract, the ventricular rate can be rapid. Indeed, if the ventricular rate in atrial fibrillation is >220 beats/min or the shortest RR interval is <250 ms, the presence of a bypass should be seriously considered because the AV node is not capable of conducting impulses at such rates in adults.
- Polymorphic VT (e.g., catecholaminergic tachycardia)
- Torsade de pointes.
In most instances, termination or slowing of
wide QRS tachycardia by vagal stimulation or
adenosine implies a supraventricular or ventricular origin?
supraventricular origin
although exceptions occur. Waxman and Wald83 reported well-documented episodes of VT that were terminated by carotid sinus massage after pretreatment with edrophonium. The subset of adenosine-sensitive idiopathic VT
criteria for VT with RBBB-like QRS morphology:
(1) in lead V1 are monophasic R or biphasic qR, QR, RS; (2) in lead V6 are rS, QS, qR.
criteria For VT with LBBB-like morphology Kindwall established the following diagnostic criteria:
(1) R wave in lead V1 or V2 >30 ms;
(2) any Q wave in V6;
(3) a duration of >=60 ms from the onset of QRS to the nadir of the S wave in V1 or V2; and
(4) notching of the downstroke of the S wave in V1 or V2.
Common to all these criteria for VT is the slow onset of the QRS complex or an abnormal Q wave.
Stierer et al analyzed the morphologic differences between VT and supraventricular tachycardia with anterograde conduction over an accessory pathway (preexcited tachycardia) with a QRS complex >0.12 second in 149 consecutive VTs and 149 consecutive preexcited regular tachycardia. They found that the following characteristics were specific for VT but were absent with preexcited tachycardia:
(1) predominantly negative QRS complexes in leads V4–V6;
(2) presence of a QR complex in one or more leads V2–V6; and
(3) more QRS complexes than P waves (when AV dissociation was present during VT).
The sensitivity and specificity of these three markers of VT were 75 percent and 100 percent, respectively.
In the so-called TYPICAL case of type I seconddegree AV block, the greatest increment of PR prolongation takes place in the _____ conducted impulse after the pause
second
Because of the periodic pauses, the rhythm has
a character of “group beating,” a finding that is an important clue to the diagnosis of Wenckebach
phenomenon.
how can atropine and carotid massage help distinguish infrahisian vs infranodal block?
Often intrahisian block can be distinguished from intranodal block on the body surface ECG, because with infrahisian block the AV conduction ratio worsens after atropine administration (which increases the sinus rate) and improves with carotid sinus massage (which decreases the sinus rate), whereas opposite effects are observed if the block is intranodal.
If the pacemaker is high in the AV junction, the ventricular rate may be increased/ decreased? by exercise or vagolytic agents?
increased
so basta sympathetic increases ventricular rate if pace maker is high in the av junc
An escape rhythm from the ventricle or low AV junction is generally not affected by such maneuvers
If the block is high grade or complete, the escape rhythm is usually junctional or his bundle vs ventricular in origin?
junctional
As a rule, the AV block is transient, and normal conduction resumes within less than 1 week after the acute episode
Most common cause of chronic AV block in Chous
Idiopathic bilateral bundle branch fibrosis
maximum heart rate usually occurs during _______ and the min heart rate at _____
The maximum heart rate usually occurs during late morning the minimum heart rate at 3 to 5 AM
thought to be the most common ectopic tachycardia seen on the ambulatory ECG
atrial tachycardia
The heart rate is generally 100 to 150 beats/min. The rhythm is often slightly irregular, with a gradual increase in rate (warming-up phenomenon), suggesting that the tachycardia is probably automatic.
The latter has been referred to as benign slow paroxysmal atrial tachycardia or ectopic atrial tachycardia The term suggested by Chou8 is accelerated atrial rhythm. With rare exception it is asymptomatic.
Arrhythmias capable of producing cardiogenic syncope include bradycardia of <___ beats/min, tachycardia of >___beats/min, and asystole longer than ___ seconds, depending on the patient’s body position and activity at the time of the arrhythmia.
< 40 bpm
> 150 bpm
3-5 sec
Because of the abnormal sequence of ventricular activation and contraction, ventricular tachycardia can often cause cerebral symptoms at a rate as low as ___ beats/min whereas patients with supraventricular tachycardia can tolerate faster rates.
120
it is generally agreed that transient ST segment elevation of ___ mm or more on the ambulatory ECG is a highly specific sign for myocardial ischemia, as it seldom occurs in normal persons without symptoms.
1mm
This study also demonstrated that isolated T wave inversion on the ambulatory ECG is a nonspecific finding, as 36 percent of the normal subjects had such a finding intermittently
Tilted p waves are seen in
hypokalemia
Serious ventricular arrhythmias are usually associated with ST segment elevation in the ____ leads, whereas bradyarrhythmias are usually associated with ST elevation in the ____ leads
anterior
inferior
In patients with chronic obstructive lung disease, ambulatory ECG recording documented a 72 percent incidence of arrhythmia, most commonly __________
multiform PVCs
The incidence of atrial arrhythmia in this study was 52 percent. In hospitalized patients, however, supraventricular arrhythmias are more common
The shape of the normal Twave is largely determined by the asynchrony of phase __
of the ventricular acti on potentials
3
The most typical ECG abnormalities in patients with mitral valve prolapse
flattening or inversion of T waves in leads II, III, and aVF with or without ST segment depression.
most common causes of global t wave inversion
The most common causes were myocardial ischemia and central nervous system disorders
The T wave abnormalities produced by hyperventilation were always accompanied by _______
tachycardia but could not be attributed solely to a critical increase in heart rate.
A decrease in T wave amplitude or T wave inversion in leads I, II, and V2–V4 occurs frequently within 30 minutes after a meal of about _____ calories
1200 calories
expected ECG abnormalities after injecting contrast material into coronary arteries
Injection of ionic contrast material into coronary arteries produces transient prolongation of the QTc interval and changes in T wave morphology
After pacing the endocardial surface of the right ventricle, or the epicardial surface and apex of the left ventricle, abnormal T waves appear predominantly in leads ______ but after pacing the right ventricular outflow tract, the T wave inversions occur mainly in leads ____
The site of stimulation determines the vector of the T wave. After pacing the endocardial surface of the right ventricle, or the epicardial surface and apex of the left ventricle, abnormal T waves appear predominantly in leads II, III, and V3–V5; but after pacing the right ventricular outflow tract, the T wave inversions occur mainly in leads V1 and V2.50
Causes of MARKED qtc lengthening
Implicated genes in Jervell and Lange -Nielsen syndrome
The Jervell and Lange-Nielsen syndrome is caused by two genes that encode the slowly activating delayed rectifier potassium channel (KCNQ1) and KCNEI
Implicated genes in Romano Ward Syndrome
Romano-Ward syndrome is caused by mutations in eight different genes. These include: KCNQI (LQTI), KCNH2(LQT2), SCN5A (sodium channel- LQT3), ANKB (protein ankyrin involved in anchoring calcium and sodium channel to the cellular membrane (LQT4), KCNEI (mink, LQT5), KCNE 2 (LQT6), KCNJ2(LQT7, Andersen’s syndrome), and CACNAIC (LQT8, Timothy syndrome).
The QT is considered short when it is <
330 ms.
possible causes of inc U wave amplitude
Positive inotropic interventions (e.g., catecholamines, calcium, digitalis, or postextrasystolic potentiation) tend to increase the U wave amplitude.
The most common type of alternans is
between left bundle branch pattern and either a normal or left ventricular hypertrophy pattern
QRS alternans during narrow QRS tachycardia suggests
QRS alternans during narrow QRS tachycardia suggests AV reentry through a manifest or concealed accessory pathway;
alternans of the ST segment elevation suggests ________
; and alternans of the ST segment elevation suggests coronary spasm. .
Other notes: alternating PR intervals may reveal dual AV nodal conduction pathways
T wave alternans in association with a long QT interval suggests
conveys a threat of torsade de pointes
Definition of gap phenomenon
The term “gap” of conduction defines a zone within the cardiac cycle during which premature impulses fail to propagate, whereas premature responses outside that zone (i.e. earlier or later) evoke propagated responses.
A correct ECG diagnosis of hyperkalemia can usually be made when plasma K concentrations exceed ____
6.7 mM.
When the plasma K concentration exceeds ___mM, the P wave amplitude usually decreases, and the duration of the P wave increases because of the slower conduction in the atria.
7.0
When the plasma K concentration exceeds about ___ mM, the P wave frequently becomes invisible
8.0
When the plasma K concentration exceeds about ____, the ventricular rhythm may become irregular owing to the simultaneous activity of several escape pacemakers in the depressed myocardium.
10 mM
An increase in the plasma K concentration to above ____ mM causes ventricular asystole or ventricular fibrillation.
12-14
Criteria by Surawicz et al for dx of hypokalemia
(1) depression of the ST segment of >=0.5 mm; (2) U wave amplitude >1 mm; and (3) U wave amplitude greater than the T wave amplitude in the same lead.
The ECG was considered to be “typical” of hypokalemia if three or more of these features were present in the two leads; it was considered “compatible” with hypokalemia if two of these features or one related to the U wave were present
Changes in extracellular calcium concentration have a profound effect on the duration of the plateau (phase ____) of the action potential.
2
In the presence of hypercalcemia associated with hypokalemia, a short QT interval with increased U wave amplitude results in a distinct pattern, most often seen in patients with ________
multiple myeloma
Hypocalcemia usually can be recognized on the ECG because, with the possible exception of _____, there are no other agents or metabolic abnormalities that prolong the duration of the ST segment without changing the duration of the T wave (a possible exception to this statement may be LQT3 pattern;
hypothermia
Which has more effect on ECG total calcium or iCa?
iCa
Because the ECG is affected by the concentration of ionized calcium rather than total calcium, it apparently correlates better with the calcium concentration in the protein-free cerebrovascular fluid than with the calcium concentration in the blood
Hypothermia is frequently associated with the appearance of a ___ wave, which is a slow upright deflection between the end of the QRS complex and the early portion of the ST segment
J wave (also called an Osborne wave)
ECG findings associated with quinidine
The ECG findings consist of the following:
1. Decreased amplitude of the T wave or
T wave inversion
2. ST segment depression
3. Prominent U waves
4. Prolongation of the QTc interval
5. Notching and widening of the P waves
6. Increased QRS duration
** Prolongation of the PR interval represents a late toxic change and occurs only when the serum concentration of quinidine reaches a high level, usually above 10 mg/L.
The most common ECG changes caused by the phenothiazines
widening, flattening, notching, or inversion of the Twave; prolongation of the QTc interval; and prominence of the U wave
The most common ECG changes associated with therapeutic doses of lithium carbonate are
T wave abnormalities
Flattening or occasional inversion of the T wave is seen in 20 to 30 percent of lithium-treated patients
The QT interval is not prolonged, and the T wave changes are reversible within 2 weeks after the drug is discontinued.
ECG changes associated with TCA toxicity
found that the presence of sinus tachycardia, prolonged QRS duration, prolonged QTc interval, and rightward shift of the terminal 40-ms QRS vector are useful ECG signs of tricyclic antidepressant cardiotoxicity. Their absence practically rules out overdose of the drug.
ECG changes associated with digitalis
The most common digitalis effects on the ECG are as follows:
1. Prolonged PR interval
2. ST segment depression
3. Decreased amplitude of the T wave, which may become diphasic (negative-positive) or negative 4. Shortened QT interval
5. Increased U wave amplitude
Earliest ecg manifestation of digitalis toxicity
Ventricular ectopic complexes are the most common arrhythmias and often represent the earliest manifestation of digitalis intoxication.
** In patients with sinus rhythm, slight prolongation of the PR interval is generally considered to be a therapeutic effect; more marked prolongation of the PR interval should be considered a warning sign of toxicity. Second- and third-degree AV block, when caused by digitalis, can be viewed as definitive evidence of intoxication.
digoxin level >____ is generally considered indicative of digitalis overdosage.
2 ng/mL
If the basic rhythm is ______ in origin, a PVC is typically followed by a pause that is fully compensatory.
sinus
Most authors use the adjective frequent when there are ___or more PVCs per minute on the routine ECG or more than _____ per hour during
ambulatory monitoring
5
10-30
Other name for PVC in triplets
Salvos
_____ comprise the most common arrhythmia in patients with mitral valve prolapse syndrome.
PVCs
most common arrhythmias in patients with digitalis excess
frequent PVCs
The pacemakers with the slowest intrinsic rate are the ______ with the gentlest slope of diastolic depolarization,
ventricular Purkinje fibers
An ectopic ventricular rhythm with a rate below 110 beats/min is generally referred to as _____
accelerated ventricular rhythm or nonparoxysmal ventricular tachycardia
When the ventricular rate is more than 200 beats/min and the tracing resembles a continuous sine wave, the rhythm is usually called ventricular flutter.
Other name for fusion beats
Dressler’s beat
In the presence of myocardial infarction, VT nearly always arises in the ____________
left ventricle or intraventricular septum
Positive concordance is seen only in VTs arising at the ___________ and negative concordance is seen only in VTs originating near
Positive: base of the heart (left ventricular outflow tract along the mitral or aortic valves, or the basal septum)
Negative: the apical septum
Involved gene in Catecholaminergic polymorphic VT
Mutations in RYR
Most common type of idiopathic VT
Idiopathic right ventricular tachycardia is the most common type, found in about 70 percent of patients.
Most prevalent form of idiopathic Left VT
The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of the left posterior fascicle of the left bundle
most common indication for permanent pacemaker implantation,
Sinus node dysfunction is the most common indication for permanent pacemaker implantation, accounting formore than 50 percent of implants.
The most common site for implantation of a permanent endocardial atrial pacing lead is the ________
right atrial appendage
most common demand pacing
VVI
2 types of AV sequential pacing mode
The AV sequential pacing mode is a dual-chamber pacing mode that paces both the atrium and the ventricle but senses only the ventricle (DVI), or it senses both atrium and ventricle but is capable only of inhibiting pacing but not triggering it (DDI)
pacing mode that is most appropriate for patients with normal sinus rhythm and AV block.
DDD
What is cross talk
Unique to the DDD (and DVI) pacemakers is the phenomenon of cross talk, or self-inhibition. Cross talk is the inappropriate sensing by one channel of electrical events generated in the other channel This is seen more commonly as detection of atrial activity or atrial stimulus by the ventricular lead.
