Interrelationship of variable coupling, multiformity and repetitive forms: implications for classification of ventricular arrhythmias

Increased variability of the coupling interval of premature ventricular contractions as a predictor of cardiac mortality in patients with left ventricular dysfunction

BACKGROUND

The characteristics and prognostic value of the variability of premature ventricular contraction (PVC) coupling intervals (CIs) for cardiac mortality are not yet decisive.

METHODS AND RESULTS

In 133 consecutive patients (58±14 years old, 53 women) who had left ventricular dysfunction (LVD: ejection fraction <50%) and frequent PVCs (≥10/h) who underwent 24-h ambulatory electrocardiography (AECG) recording and (123)I-metaiodobenzylguanidine myocardial single-photon emission computed tomography simultaneously, the heart rate turbulence onset, slope, and T-wave alternans were analyzed from the 24-h AECG. The CI of the PVCs (MEANNV), standard deviation of the CI of the PVCs (SDNV) as an index of the variability of the PVC CI, and their ratio to the preceding N-N intervals (SDNV/SDNN) were calculated from constructed Poincaré plots using the annotated 24-h AECG QRS data. The primary endpoint was cardiac mortality. The mean follow-up period was 63 months. Among 133 patients, 114 survived (group 1) and 19 (14%, group 2) died during the follow-up. The MEANNVand SDNVwere higher in group 2 (539±104 vs. 599±114 ms, P=0.021; 64±34 vs. 83±37 ms, P=0.022, respectively). The SDNV, PVC count, and delayed heart/mediastinum ratio remained as significant predictors of cardiac mortality in the binary logistic regression analysis.

CONCLUSIONS

These results suggest that the SDNVcould be another adjunctive parameter for predicting cardiac mortality in LVD.

Increased variability of the coupling interval of premature ventricular beats may help to identify high-risk patients with coronary artery disease

OBJECTIVE

The purpose of this study was to determine the characteristics and predictive value of the variability of coupling interval of ventricular premature beats (VPBs) for cardiac mortality in patients with coronary artery disease (CAD).

BACKGROUND

Frequent VPBs have been linked to an increased risk for cardiac death in patients with coronary artery disease. It is unknown whether analysis of coupling interval of VPBs from ambulatory ECG recordings can be used for risk statification in these patients.

METHODS

In 78 consecutive symptomatic patients with documented CAD who presented with frequent VPBs (>720/24 h), the analysis of VPBs' coupling interval (SDNV) was performed. Left ventricular function, ventricular arrhythmias and simple measures of heart rate variability were assessed. Mean follow-up was 702+/-329 days. Cardiac mortality was the primary end-point of the study.

RESULTS

During follow-up, 14 patients died-11 deaths were cardiac. Left ventricular ejection fraction (LVEF)<40%; no beta-blocker treatment and digoxin use were clinical variables showing a significant association with cardiac mortality. The presence of non-sustained ventricular tachycardia (nsVT), especially if more than five episodes were present; short mean sinus cycle (<750 ms) and SDNV were associated with cardiac deaths. Mean SDNV was 79+/-29 in victims and 63+/-29 in survivors (p<0.05). Univariate Cox regression analysis revealed that the presence of SDNV>80 ms carried a relative risk of 6.7 for cardiac mortality. The adjusted relative risk was 13.3 for nsVT and 4.4 for SDNV>80 ms. Among patients with nsVT, mortality rate was significantly higher with SDNV>80 ms (58%), compared to lower SDNV (14%, p<0.01). Sixty-four percent mortality rate was observed in patients with LVEF<40%, presence of nsVT and SDNV>80 ms, compared to 17% in similar patients with lower SDNV (p<0.05).

CONCLUSION

The analysis of coupling interval of ventricular premature beats form the same 24-h ECG recordings may complement the standard Holter analysis for risk stratification. This seems especially promising in the subgroups of patients at highest risk-those with LV systolic dysfunction, non-sustained VT or both.

Ventricular beat classifier using fractal number clustering

A two-stage ventricular beat 'associative' classification procedure is described. The first stage separates typical beats from extrasystoles on the basis of area and polarity rules. At the second stage, the extrasystoles are classified in self-organised cluster formations of adjacent shape parameter values. This approach avoids the use of threshold values for discrimination between ectopic beats of different shapes, which could be critical in borderline cases. A pattern shape feature conventionally called a 'fractal number', in combination with a polarity attribute, was found to be a good criterion for waveform evaluation. An additional advantage of this pattern classification method is its good computational efficiency, which affords the opportunity to implement it in real-time systems.