Heart rate changes preceding ventricular ectopy in patients with ventricular tachycardia caused by reentry, triggered activity, and automaticity

ECG Markers of Acute Melatonin Treatment in a Porcine Model of Acute Myocardial Ischemia

In myocardial ischemia, melatonin confers antiarrhythmic action, but its electrocardiographic expression is unclear. We aimed to evaluate the effects of melatonin treatment on electrocardiogram (ECG) parameters reflecting major arrhythmogenic factors and to test the association of these parameters with ventricular fibrillation (VF) incidence. Myocardial ischemia was induced by 40 min coronary artery occlusion in 25 anesthetized pigs. After induction of ischemia, 12 and 13 animals were given melatonin or placebo, respectively. Twelve-lead ECGs were recorded and durations of QRS, QT, Tpeak-Tend intervals and extrasystolic burden were measured at baseline and during occlusion. During ischemia, VF episodes clustered into early and delayed phases (<10 and >20 min, respectively), and QRS duration was associated with VF incidence. QT interval and extrasystolic burden did not differ between the groups. The Tpeak-Tend interval was progressively prolonged, and the prolongation was less pronounced in the treated animals. QRS duration increased, demonstrating two maxima (5−10 and 25 min, respectively). In the melatonin group, the earlier maximum was blunted, and VF development in this period was prevented. Thus, acute melatonin treatment prevented excessive prolongation of the QRS and Tpeak-Tend intervals in the porcine myocardial infarction model, and QRS duration can be used for the assessment of antiarrhythmic action of melatonin.

Increased heart rate due to supra-ventricular tachycardia triggering premature ventricular contraction

We describe a case wherein the presence of premature ventricular contractions was related to an increased heart rate that occurred due to supra-ventricular tachycardia: atrial tachycardia or atrioventricular nodal reentry tachycardia.

Effects of Beating- versus Arrested-Heart Revascularization on Cardiac Autonomic Regulation and Arrhythmias

BACKGROUND

Altered autonomic regulation after cardiac operations precipitates cardiac arrhythmias, affects repolarization, and increases the risk of sudden cardiac death. We sought to clarify how the 2 different techniques of coronary artery bypass grafting (CABG), namely conventional CABG using cardiopulmonary bypass (on-pump) and beating-heart CABG without cardiopulmonary bypass (off-pump), affect cardiac autonomic regulation and arrhythmic disturbances postoperatively.

METHODS

We included 57 consecutive patients, 28 in the on-pump group and 29 in the off-pump group. The electro-cardiographic recordings were performed on the preoperative day and the fourth, seventh, and twenty-eighth day after operation. Fifteen-minute digital recordings were taken; one channel was used to record electrocardiogram and the other breathing. Detailed analyses of arrhythmia, heart rate, and heart rate variability indices were performed on respective days to assess sympathetic and parasympathetic modulation of the heart and relate it to detected arrhythmic disturbances.

RESULTS

Total power, low-frequency power, which indicates baroreceptor-mediated sympathetic modulation, and high-frequency power, indicating parasympathetic vagal modulation, declined significantly in both groups after CABG (P < .001); however, 7 days after CABG, total and high-frequency power were better preserved in the off-pump group. Mean RR interval was longer in the off-pump group at 7 (P= .006) and 28 days (P= .008) after surgery. The total incidence of arrhythmic events was higher in the on-pump group on the seventh day (P = .017, adjusted odds ratio = 8.6, 95% confidence interval 1.4-80.3).

CONCLUSIONS

The results show profound impairment of cardiac autonomic regulation after CABG, showing better preserved cardiac autonomic modulation 7 days after beating-heart revascularization. Evidence suggests that slower restoration of heart rate and increased incidence of arrhythmic events after CABG using cardiopulmonary bypass are the result not only of impaired cardiac autonomic regulation but also of the involvement of additional factors of nonautonomic origin.

Prognostic significance of PVCs and resting heart rate

BACKGROUND

We sought to evaluate the prognostic significance of premature ventricular contractions (PVCs) on a routine electrocardiogram (ECG) and to evaluate the relationship between heart rate and PVCs.

METHODS

Computerized 12-lead ECGs of 45,402 veterans were analyzed. Vital status was available through the California Health Department Service.

RESULTS

There were 1731 patients with PVCs (3.8%). Compared to patients without PVCs, those with PVCs had significantly higher all-cause (39% vs 22%, P < 0.001) and cardiovascular mortality (20% vs 8%, P < 0.001). PVCs remain a significant predictor even after adjustment for age and other ECG abnormalities. The presence of multiple PVCs or complex morphologies did not add significant additional prognostic information. Those patients with PVCs had a significantly higher heart rate than those without PVCs (mean +/- SD: 78.6 +/- 15 vs 73.5 +/- 16 bpm, P < 0.001). When patients were divided into groups by heart rate (<60, 60-79, 80-99 and >100 bpm) and by the presence or absence of PVCs, mortality increased progressively with heart rate and doubled with the presence of PVCs. Using regression analysis, heart rate was demonstrated to be an independent and significant predictor of PVCs.

CONCLUSIONS

PVCs on a resting ECG are a significant and independent predictor of all-cause and cardiovascular mortality. Increased heart rate predicts mortality in patients with and without PVCs and the combination dramatically increases mortality. These findings together with the demonstrated independent association of heart rate with PVCs suggest that a hyperadrenergic state is present in patients with PVCs and that it likely contributes to their adverse prognosis.

Persistent atrial fibrillation is associated with appropriate shocks and heart failure in patients with left ventricular dysfunction treated with an implantable cardioverter defibrillator

AIM

The objective of this study was to investigate whether persistent atrial fibrillation (AF) and new-onset AF are associated with appropriate shocks, cardiovascular mortality, chronic heart failure (CHF), and inappropriate shocks in implantable cardioverter defibrillator (ICD) patients with left ventricular dysfunction.

METHODS

We included 290 consecutive ICD patients with a documented left ventricular ejection fraction < or = 0.35 and compared outcomes between patients without AF (n = 207), those with persistent AF (n = 64), and those with new-onset AF (n = 19).

RESULTS

The patients with persistent AF were older, more frequently had valve disease and cardiac surgery, and less frequently had coronary artery disease as compared with the patients without AF. Patients with persistent AF had a higher New York Heart Association class, however, left ventricular ejection fraction rates between these 2 groups were comparable (0.28 +/- 0.07 vs 0.29 +/- 0.08, P = not significant). No difference was found between patients with new-onset AF and those without AF. During follow-up (2.6 +/- 1.9 years), more patients with persistent AF received appropriate ICD shocks as compared with those without AF (24 [38%] vs 49 [24%], P = .04). Deterioration of CHF occurred more often in patients with persistent AF (19 [30%], P = .001) and those with new-onset AF (9 [47%], P < .001) as compared with patients without AF (31 [14%]). Multivariate analysis revealed that patients with persistent AF had an increased risk for appropriate ICD shocks (adjusted hazard ratio [HR] 1.9, 95% CI 1.2-3.2, P = .009). Persistent AF (adjusted HR 2.1, 95% CI 1.1-3.9, P = .03) and new-onset AF (adjusted HR 2.5, 95% CI 1.1-5.7, P = .02) were found to be independent risk indicators of CHF deterioration.

CONCLUSIONS

In ICD patients with left ventricular dysfunction, persistent AF is associated with appropriate ICD shocks and deterioration of CHF. New-onset AF is related to deterioration of CHF.

Markers of autonomic tone on a standard ECG are predictive of mortality in old age

BACKGROUND

To investigate markers of autonomic tone on a standard electrocardiogram in relation to mortality in old age.

METHODS

A total of 599 inhabitants of Leiden, the Netherlands, were enrolled in a population-based follow-up study at their 85th birthday. Electrocardiograms (ECGs) were taken on entry and annually thereafter. ECGs were analysed automatically to determine four markers of autonomic tone, i.e. heart rate, the occurrence of ventricular extrasystoles and two time domain measures of heart rate variability. All participants were followed up for mortality.

RESULTS

Participants with a heart rate in the highest quartile had a 1.8-fold increased total mortality risk (95% confidence interval (CI) 1.0-3.4), but not an increased cardiovascular mortality risk. The occurrence of at least one ventricular extrasystole was related with a 2.3-fold increased total mortality risk (95% CI 1.3-3.9) and a 3.6-fold increased cardiovascular mortality (95% CI 1.6-8.2). In stratified analyses, the prognostic effect was confined to males. Both measures of heart rate variability were not related to mortality.

CONCLUSION

High heart rate and the occurrence of a ventricular extrasystole, both markers of sympathetic dominance, were predictive of mortality in old age. Two short-term measures of heart rate variability as measured on a standard 10-s ECG were not related to mortality, and hence may not reflect autonomic tone in old age.

Do atrial tachyarrhythmias beget ventricular tachyarrhythmias in defibrillator recipients?

OBJECTIVES

This study was designed to analyze the incidence of "dual tachycardia"-ventricular tachycardia (VT) or ventricular fibrillation (VF) preceded by paroxysmal atrial tachycardia (AT) or atrial fibrillation (AF)-in patients receiving dual-chamber implantable cardioverter defibrillators (ICDs).

BACKGROUND

Paroxysmal AT/AF occurs commonly in patients who receive ICDs for the treatment of life-threatening VT/VF. Although AF is associated with an adverse prognosis in the setting of structural heart disease, the relationship between AT/AF and VT/VF is unclear.

METHODS

We followed 537 patients undergoing implantation of the Jewel AF ICD (Model 7250, Medtronic, Minneapolis, Minnesota) for 11.4 +/- 8.2 months. These included 398 patients with a history of at least two episodes of AT or AF during the preceding year as well as 139 patients enrolled because of VT/VF alone.

RESULTS

There were 233 dual tachycardia episodes in 45 patients during follow-up. Overall, 8.9% of episodes detected as VT/VF were dual tachycardias, and 20.3% of patients with VT/VF had at least one dual tachycardia episode. The median duration of AT/AF preceding the first VT/VF detection was 1.09 h (25% to 75% quartile 0.24 to 33.4 h). When AT/AF continued between two consecutive VT/VF detections, the median interdetection interval was 11 min. When AT/AF terminated either because of a ventricular therapy or spontaneously, the median interdetection interval was prolonged to 71 h (p < 0.001).

CONCLUSIONS

Dual tachycardia is common in ICD recipients with a history of AT/AF. The duration of AT/AF preceding the first VT/VF detection is < or =1 h about 50% of the time. Termination of the AT/AF significantly delays the time to the next VT/VF detection.

Correlation and stability of heart rate and ventricular ectopy variability in patients with congestive heart failure

The stability of indexes of heart rate variability and their possible association with spontaneous variability of ventricular ectopy was examined in 13 patients with advanced congestive heart failure over 14 consecutive days of 24-hour ambulatory electrocardiographic recording. It was found that time and frequency domain measures of heart rate variability are stable over time and are inversely correlated with spontaneous variability of ventricular ectopy.