Chou's

Question 1

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

Answer 1

Concertina effect

Question 2

The WPW ECG pattern with full preexciation
contains the following elements:

Answer 2

1. A PR interval of less than 0.12 second,
   with a normal P wave
2. Abnormally wide QRS complex with
   a duration of 0.11 second or more
3. The presence of initial slurring of the QRS
   complex, the delta wave
4. Secondary ST segment and T wave changes

Question 3

A normal “septal” q wave is seldom found in
the preexcited complexes. Its presence in lead
__ is believed to exclude preexcitation.

Answer 3

V6

Question 4

The WPW pattern occurs more often in males/females?

Answer 4

males

Question 5

most important clinical manifestations in patients with WPW syndrome

Answer 5

Paroxysmal tachycardias

Paroxysmal supraventricular tachycardia is responsible for 75 to 80 percent of all paroxysmal tachycardias in patients with WPW syndrome.

Question 6

Diagnostic criteria on the surface ECG and in the intracardiac electrogram during tachycardia include the following for orthodromic reentry tachycardia

Answer 6

(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

Question 7

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

Answer 7

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

Question 7

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.

Answer 7

“paradoxical capture.

Question 8

The anterograde effective refractory period is the longest A1A2 interval recorded nearest the AP at which A2 conducts to ventricles without preexcitation.

Question 9

the longest V1V2 interval recorded nearest the AP with the activation sequence compatible with retrograde conduction through the accessory bypass tract.

Answer 9

retrograde effective refractory period

Question 10

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

Answer 10

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

Question 11

findings during tachycardia to be suggestive of a concealed bypass tract

Answer 11

(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

Question 12

Conditions favorable for development of antidromic tachycardia include:

Answer 12

(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.

Question 13

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?)

Answer 13

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

Question 14

Nodofascicular tachycardia should be suspected if:

Answer 14

(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

Question 15

Drugs that can shorten effective refractory period of accessory pathways

Answer 15

Digitalis
beta blockers
CCB eg verapamil and diltiazem

Question 16

Drugs that can prolong effective refractory period of accessory pathways

Answer 16

refractoriness is prolonged by class IA and class III antiarrhythmia drugs.

Question 17

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

Answer 17

(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.

Question 18

The risk is increased with increasing QTc duration and in the presence of

Answer 18

(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.

Question 19

Many experimental studies suggest that TDP is initiated by a process known as ________ , which may also contribute to maintenance of the arrhythmia.

Answer 19

early afterdepolarizations

Question 20

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.

Answer 20

commotio cordis

Question 21

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:

Answer 21

1. Ventricular tachycardia
2. Aberrant ve ntricular conduction
3. Preexisting left (LBBB) or right (RBBB) bundle branch block
4. Preexisting nonspecific intraventricular conduction defect
5. Anterograde conduction through the bypass tract in patients with the Wolff-Parkinson- White (WPW) syndrome
6. Anterograde conduction over an atriofascicular
   or nodoventricular connection

Question 22

An irregular wide QRS complex tachycardia may represent one of the following rhythms:

Answer 22

1. Atrial fibrillation with aberrant ventricular conduction, bundle branch block, or intraventricular conduction defect.
2. 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.
3. Polymorphic VT (e.g., catecholaminergic tachycardia)
4. Torsade de pointes.

Question 23

In most instances, termination or slowing of
wide QRS tachycardia by vagal stimulation or
adenosine implies a supraventricular or ventricular origin?

Answer 23

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

Question 24

criteria for VT with RBBB-like QRS morphology:

Answer 24

(1) in lead V1 are monophasic R or biphasic qR, QR, RS; (2) in lead V6 are rS, QS, qR.

Question 25

criteria For VT with LBBB-like morphology Kindwall established the following diagnostic criteria:

Answer 25

(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.

Question 26

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:

Answer 26

(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.

Question 27

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

Answer 27

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.

Question 28

how can atropine and carotid massage help distinguish infrahisian vs infranodal block?

Answer 28

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.

Question 29

If the pacemaker is high in the AV junction, the ventricular rate may be increased/ decreased? by exercise or vagolytic agents?

Answer 29

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

Question 30

If the block is high grade or complete, the escape rhythm is usually junctional or his bundle vs ventricular in origin?

Answer 30

junctional As a rule, the AV block is transient, and normal conduction resumes within less than 1 week after the acute episode

Question 31

Most common cause of chronic AV block in Chous

Answer 31

Idiopathic bilateral bundle branch fibrosis

Question 32

maximum heart rate usually occurs during _______ and the min heart rate at _____

Answer 32

The maximum heart rate usually occurs during late morning the minimum heart rate at 3 to 5 AM

Question 33

thought to be the most common ectopic tachycardia seen on the ambulatory ECG

Answer 33

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.

Question 34

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.

Answer 34

< 40 bpm > 150 bpm 3-5 sec

Question 35

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.

Answer 35

120

Question 36

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.

Answer 36

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

Question 37

Tilted p waves are seen in

Answer 37

hypokalemia

Question 38

Serious ventricular arrhythmias are usually associated with ST segment elevation in the ____ leads, whereas bradyarrhythmias are usually associated with ST elevation in the ____ leads

Answer 38

anterior inferior

Question 39

In patients with chronic obstructive lung disease, ambulatory ECG recording documented a 72 percent incidence of arrhythmia, most commonly __________

Answer 39

multiform PVCs The incidence of atrial arrhythmia in this study was 52 percent. In hospitalized patients, however, supraventricular arrhythmias are more common

Question 40

The shape of the normal Twave is largely determined by the asynchrony of phase __ of the ventricular acti on potentials

Answer 40

3

Question 41

The most typical ECG abnormalities in patients with mitral valve prolapse

Answer 41

flattening or inversion of T waves in leads II, III, and aVF with or without ST segment depression.

Question 42

most common causes of global t wave inversion

Answer 42

The most common causes were myocardial ischemia and central nervous system disorders

Question 43

The T wave abnormalities produced by hyperventilation were always accompanied by _______

Answer 43

tachycardia but could not be attributed solely to a critical increase in heart rate.

Question 44

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

Answer 44

1200 calories

Question 45

expected ECG abnormalities after injecting contrast material into coronary arteries

Answer 45

Injection of ionic contrast material into coronary arteries produces transient prolongation of the QTc interval and changes in T wave morphology

Question 46

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 ____

Answer 46

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

Question 47

Causes of MARKED qtc lengthening

Answer 47

Question 48

Implicated genes in Jervell and Lange -Nielsen syndrome

Answer 48

The Jervell and Lange-Nielsen syndrome is caused by two genes that encode the slowly activating delayed rectifier potassium channel (KCNQ1) and KCNEI

Question 49

Implicated genes in Romano Ward Syndrome

Answer 49

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).

Question 50

The QT is considered short when it is <

Answer 50

330 ms.

Question 51

possible causes of inc U wave amplitude

Answer 51

Positive inotropic interventions (e.g., catecholamines, calcium, digitalis, or postextrasystolic potentiation) tend to increase the U wave amplitude.

Question 52

The most common type of alternans is

Answer 52

between left bundle branch pattern and either a normal or left ventricular hypertrophy pattern

Question 53

QRS alternans during narrow QRS tachycardia suggests

Answer 53

QRS alternans during narrow QRS tachycardia suggests AV reentry through a manifest or concealed accessory pathway;

Question 54

alternans of the ST segment elevation suggests ________

Answer 54

; and alternans of the ST segment elevation suggests coronary spasm. . Other notes: alternating PR intervals may reveal dual AV nodal conduction pathways

Question 55

T wave alternans in association with a long QT interval suggests

Answer 55

conveys a threat of torsade de pointes

Question 56

Definition of gap phenomenon

Answer 56

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.

Question 57

A correct ECG diagnosis of hyperkalemia can usually be made when plasma K concentrations exceed ____

Answer 57

6.7 mM.

Question 58

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.

Answer 58

7.0

Question 59

When the plasma K concentration exceeds about ___ mM, the P wave frequently becomes invisible

Answer 59

8.0

Question 60

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.

Answer 60

10 mM

Question 61

An increase in the plasma K concentration to above ____ mM causes ventricular asystole or ventricular fibrillation.

Answer 61

12-14

Question 62

Criteria by Surawicz et al for dx of hypokalemia

Answer 62

(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

Question 63

Changes in extracellular calcium concentration have a profound effect on the duration of the plateau (phase ____) of the action potential.

Answer 63

2

Question 64

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 ________

Answer 64

multiple myeloma

Question 65

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;

Answer 65

hypothermia

Question 66

Which has more effect on ECG total calcium or iCa?

Answer 66

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

Question 67

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

Answer 67

J wave (also called an Osborne wave)

Question 68

ECG findings associated with quinidine

Answer 68

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.

Question 69

The most common ECG changes caused by the phenothiazines

Answer 69

widening, flattening, notching, or inversion of the Twave; prolongation of the QTc interval; and prominence of the U wave

Question 70

The most common ECG changes associated with therapeutic doses of lithium carbonate are

Answer 70

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.

Question 71

ECG changes associated with TCA toxicity

Answer 71

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.

Question 72

ECG changes associated with digitalis

Answer 72

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

Question 73

Earliest ecg manifestation of digitalis toxicity

Answer 73

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.

Question 74

digoxin level >____ is generally considered indicative of digitalis overdosage.

Answer 74

2 ng/mL

Question 75

If the basic rhythm is ______ in origin, a PVC is typically followed by a pause that is fully compensatory.

Answer 75

sinus

Question 76

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

Answer 76

5 10-30

Question 77

Other name for PVC in triplets

Answer 77

Salvos

Question 78

_____ comprise the most common arrhythmia in patients with mitral valve prolapse syndrome.

Answer 78

PVCs

Question 79

most common arrhythmias in patients with digitalis excess

Answer 79

frequent PVCs

Question 80

The pacemakers with the slowest intrinsic rate are the ______ with the gentlest slope of diastolic depolarization,

Answer 80

ventricular Purkinje fibers

Question 81

An ectopic ventricular rhythm with a rate below 110 beats/min is generally referred to as _____

Answer 81

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.

Question 82

Other name for fusion beats

Answer 82

Dressler's beat

Question 83

In the presence of myocardial infarction, VT nearly always arises in the ____________

Answer 83

left ventricle or intraventricular septum

Question 84

Positive concordance is seen only in VTs arising at the ___________ and negative concordance is seen only in VTs originating near

Answer 84

Positive: base of the heart (left ventricular outflow tract along the mitral or aortic valves, or the basal septum) Negative: the apical septum

Question 85

Involved gene in Catecholaminergic polymorphic VT

Answer 85

Mutations in RYR

Question 86

Most common type of idiopathic VT

Answer 86

Idiopathic right ventricular tachycardia is the most common type, found in about 70 percent of patients.

Question 87

Most prevalent form of idiopathic Left VT

Answer 87

The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of the left posterior fascicle of the left bundle

Question 88

most common indication for permanent pacemaker implantation,

Answer 88

Sinus node dysfunction is the most common indication for permanent pacemaker implantation, accounting formore than 50 percent of implants.

Question 89

The most common site for implantation of a permanent endocardial atrial pacing lead is the ________

Answer 89

right atrial appendage

Question 90

most common demand pacing

Answer 90

VVI

Question 91

2 types of AV sequential pacing mode

Answer 91

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)

Question 92

pacing mode that is most appropriate for patients with normal sinus rhythm and AV block.

Answer 92

DDD

Question 93

What is cross talk

Answer 93

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.