Initiation of monomorphic ventricular tachycardia: electrophysiological, clinical features, and drug therapy in patients with implantable defibrillators

Defining the pattern of initiation of monomorphic ventricular tachycardia using the beat-to-beat intervals recorded on implantable cardioverter defibrillators from the RAFT study: A computer-based algorithm

Arrhythmia onset pattern may have important implications on morbidity, recurrent implantable cardioverter defibrillator (ICD) shocks, and mortality, given the proposed correlation between initiation pattern and arrhythmia mechanism. Therefore, we developed and tested a computer-based algorithm to differentiate the pattern of initiation based on the beat-to-beat intervals of the ventricular tachycardia (VT) episodes in ICD recordings from the Resynchronization-Defibrillation for Ambulatory Heart Failure Trial (RAFT). Intervals on intracardiac electrograms from ICDs were analyzed backwards starting from the marker of VT detection, comparing each interval with the average tachycardia cycle length. If the morphology of the beat initiating the VT was similar to the morphology of the VT itself, the episode was considered sudden. If the morphology of the beat initiating the VT was not similar to the morphology of the VT itself, the episode was considered non-sudden. The capability of the algorithm to classify the pattern of initiation based only on the beat-to-beat intervals allows for the classification and analysis of large datasets to further investigate the clinical importance of classifying VT initiation. If analysis of the VT initiation proves to be of clinical value, this algorithm could potentially be integrated into ICD software, which would make it easily accessible and potentially helpful in clinical decision-making.

Hemodynamic deterioration precedes onset of ventricular tachyarrhythmia after Heartmate II implantation

Background

Early postoperative ventricular tachyarrhythmia (PoVT) after left ventricular assist device (LVAD) implantation are common and associated with higher mortality-rates. At present, there is no data on initiation of these PoVT and the role of alterations in cardiac hemodynamics.

Case Presentation

A LVAD was implanted in a patient with end-stage heart failure due to a ischemic cardiomyopathy. Alterations in cardiac rhythm and hemodynamics preceding PoVT-episodes during the first five postoperative days were examined by using continuous recordings of cardiac rhythm and various hemodynamic parameters. All PoVT (N=120) were monomorphic, most often preceded by short-long-short-sequences or regular SR and initiated by ventricular runs. Prior to PoVT, mean arterial pressure decreased; heart rate and ST-segments deviations increased.

Conclusions

PoVT are caused by different underlying electrophysiological mechanisms. Yet, they are all monomorphic and preceded by hemodynamic deterioration due to myocardial ischemia.

Mode of onset of polymorphic ventricular tachycardia in acute myocardial infarction

BACKGROUND

Polymorphic ventricular tachycardia (PVT) can occur during acute myocardial infarction (MI). In the past, studies investigated the initiation pattern of ventricular tachycardias in different patient populations; however, the mode of onset of PVT in acute MI patients has not been investigated previously.

OBJECTIVE

To retrospectively investigate the electrophysiological features of PVT with different initiation patterns in acute MI patients to assess whether there is a relationship of the initiation patterns of PVT with clinical and electrophysiological characteristics.

METHODS

Sixty-two rhythm strips defined as PVT from 53 patients (mean [± SD] age 63±8 years) with acute ST elevation MI were analyzed. All patients were monitored while they were hospitalized in the coronary care unit, and the electrocardiogram strips were obtained from continuous monitoring. PVT was defined as sudden-onset tachycardia if it was not preceded by ventricular ectopic beats. PVT that was preceded by single or multiple ectopic beats was defined as nonsudden-onset tachycardia.

RESULTS

Nonsudden-onset episodes were more common than suddenonset episodes (40 episodes [64.5%] versus 22 episodes [35.5%]). In the nonsudden-onset group, 25 episodes (62.5%) were initiated after a single ectopic beat, while 15 episodes (37.5%) were initiated after multiple complexes. The mean (± SD) left ventricular ejection fraction of patients with nonsudden-onset PVT was decreased (53±6% versus 65±7%, P<0.01). Nonsudden-onset tachycardias had lower coupling intervals than suddenonset tachycardias. Similarly, the PVT cycle length was shorter in the presence of nonsudden-onset initiation. When nonsudden-onset PVT episodes were further subclassified based on the morphology of the first beat of tachycardia, 26 PVTs (65%) had a first beat of tachycardia similar to the subsequent PVT beats and 14 (35%) did not.

CONCLUSIONS

These results demonstrate that PVT is often preceded by ventricular ectopy in acute MI patients. Nonsudden-onset PVT is usually characterized by a lower coupling interval, shorter PVT cycle length and an associated lower ejection fraction.

Clinical importance of short-long-short sequences: analysing the mode of onset of ventricular tachycardias and atrial fibrillation

Clinical importance of atrial and ventricular ectopic beats are investigated in some experimental and clinical trials. They are common and occur in a broad spectrum of the population. This includes patients without structural heart disease and those with any form of cardiac disease, independent of severity. Although we know something about the mechanisms and etiology of serious ventricular arrhythmias and atrial fibrillation, we don't know a lot about mode of onset of those arrhythmias. Can short-long-short sequences, related ectopic beats predict AF and ventricular tachycardias in some selected groups of patients? In this paper we will try to answer this important question.

Mechanisms of ventricular fibrillation initiation in MADIT II patients with implantable cardioverter defibrillators

BACKGROUND

The availability of stored intracardiac electrograms from implantable defibrillators (ICDs) has facilitated the study of the mechanisms of ventricular tachyarrhythmia onset. This study aimed to determine the patterns of initiation of ventricular fibrillation (VF) in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II patients along with associated electrocardiogram (ECG) parameters and clinical characteristics.

METHODS

Examination of stored electrograms enabled us to evaluate the rhythm preceding each episode of VF and to calculate (intracardiac) ECG parameters including QT, QT peak (QTp), coupling interval, and prematurity index.

RESULTS

Sixty episodes of VF among 29 patients (mean age 64.4 +/- 2.5 years) were identified. A single ventricular premature complex (VPC) initiated 46 (77%) episodes whereas a short-long-short (SLS) sequence accounted for 14 (23%) episodes. Of the 29 patients studied, 23 patients had VF episodes preceded by a VPC only, two patients with SLS only, and four patients with both VPC and SLS-initiated episodes. There were no significant differences between initiation patterns in regards to the measured ECG parameters; a faster heart rate with SLS initiation (mean RR prior to VF of 655 +/- 104 ms for SLS and 744 +/- 222 ms for VPC) approached significance (P = 0.06). The two patients with SLS only were not on beta-blockers compared to 83% of the VPC patients.

CONCLUSION

Ventricular fibrillation is more commonly initiated by a VPC than by a SLS sequence among the MADIT II population. Current pacing modes designed to prevent bradycardia and pause-dependent arrhythmias are unlikely to decrease the incidence of VPC-initiated episodes of VF.

Electrophysiologic characteristics of anger-triggered arrhythmias

BACKGROUND

Anger can precipitate ventricular arrhythmias in patients with implantable cardioverter-defibrillators (ICDs). Determining electrophysiologic characteristics of anger-triggered arrhythmias may help elucidate the mechanisms that link emotion and arrhythmia.

OBJECTIVES

We sought to compare the morphology and initiation pattern between ventricular arrhythmias that are triggered by anger and those that are not.

METHODS

At the time of shock, patients with ICDs recorded levels of defined mood states preceding the shock in a diary. Stored intracardiac electrograms (EGMs) were retrieved and analyzed in relation to corresponding mood states. The EGMs from 56 appropriate shocks in 24 patients (18 male, mean age 66 years, 74% with coronary artery disease) were reviewed and analyzed for morphology, mechanism of initiation (sudden onset vs. premature ventricular contraction [PVC]), pause dependence, and other characteristics.

RESULTS

Polymorphic ventricular tachycardia was more common in anger-triggered events, occurring in three (37.5%) of eight anger-triggered events compared with five (10.4%) of 48 of non-anger-triggered events (P <.05). Anger-triggered events were more likely to have PVC initiation, occurring in eight (100%) of eight, compared with 30 (68%) of 44 of non-anger-triggered events (P <.05). More anger-triggered events were pause dependent: five (62.5%) of eight versus seven (15%) of 37 non-anger-related events (P <.01). No difference in response to initial therapy was observed in anger-triggered arrhythmias.

CONCLUSION

Ventricular arrhythmias occurring in the setting of anger are more likely pause dependent and polymorphic. This suggests that in predisposed populations anger may create an arrhythmogenic substrate susceptible to more disorganized rhythms, a possible mechanism linking emotion and sudden death.

Importance of initiation pattern of polymorphic ventricular tachycardia in patients with implantable cardioverter defibrillators

BACKGROUND

Stored intracardiac electrograms (ICEGs) are helpful in understanding the initiation mechanisms of sustained ventricular arrhythmias and in determining the appropriateness of the therapy delivered by implantable cardioverter defibrillators (ICDs).

AIM

We investigated the initiation pattern of sustained polymorphic ventricular tachycardia (PVT) and the features of the therapy delivered by ICDs.

METHODS

Sixty-six patients (mean age of 67 +/- 8 years) with 97 stored ICEGs showing PVT were evaluated. Cardiovascular diagnosis included coronary artery disease in 72.7% of the patients. The average left ventricular ejection fraction was 33+/-6%.

RESULTS

Nonsudden onset episodes were more common than sudden onset episodes (63 episodes, 65% vs 34 episodes, 35%, P < 0.001). More PVT episodes were required multiple shock delivery if they had nonsudden onset initiation (28.6% vs 23.6%, P < 0.01). The mean shock energy delivered for arrhythmia termination was higher in PVT with nonsudden onset (20 +/- 4 vs 14 +/- 5 J, P < 0.01).

CONCLUSIONS

The stored ICEGs demonstrate that PVT is most often preceded by ventricular ectopy. To be reverted, nonsudden onset episodes require higher levels of shock energy and more frequently multiple shock achievements than sudden onset episodes.

Triggers of sustained monomorphic ventricular tachycardia differ among patients with varying etiologies of left ventricular dysfunction

BACKGROUND

The mechanisms underlying the initiation of sustained ventricular tachycardia (VT) have not been fully elucidated. The extent to which reentry, abnormal automaticity, and triggered activity play a role in VT differs depending on the etiology of left ventricular dysfunction. By analyzing electrograms from implantable cardioverter defibrillator (ICD), we sought to determine whether there were differences in VT initiation patterns between patients with ischemic and nonischemic cardiomyopathy.

METHODS

We analyzed ICD electrograms in patients with ejection fractions < 40% who had sustained VT over a 27-month period. The trigger for VT onset was classified as a ventricular premature beat (VPB), supraventricular tachycardia, or of "sudden onset." The baseline cycle length, VT cycle length, coupling interval, and prematurity ratio were recorded for each event. The prematurity ratio was calculated as the coupling interval of the VT initiator divided by the baseline cycle length.

RESULTS

Sixty-three VT events in 14 patients met the inclusion criteria. A VPB initiated the VT in 58 episodes (92%), 1 episode (2%) was initiated by a supraventricular tachycardia, and 4 episodes (6%) were sudden onset. The prematurity ratio was significantly higher (P < 0.05) in patients with ischemic cardiomyopathy (0.751 +/- 0.068) as compared to patients with nonischemic cardiomyopathy (0.604 +/- 0.139).

CONCLUSION

VPBs initiated most sustained VT episodes. A significantly higher prematurity ratio was observed in the ischemic heart disease group. This may represent different mechanisms of VT initiation in patients with ischemic versus nonischemic heart disease.