Relation of ventricular tachycardia/fibrillation to beta-blocker dose maximization guided by pacing mode analysis in nonpacemaker-dependent patients with implantable cardioverter-defibrillator

We hypothesized that uptitration of β blockade and adjustment of pacing parameters to achieve a prevalence of single chamber atrial inhibited rate-responsive (AAIR) pacing in patients with dual-chamber implantable cardioverter--defibrillators (ICDs) would result in maximization of β-blocker dosage and thus decrease appropriate ICD therapies. We included patients with ischemic or dilated cardiomyopathy and implanted ICDs without contraindications to β blockers and atrioventricular conduction disturbances. Two 6-month periods were compared: clinically guided phase (pacing function set at back-up dual-chamber rate-responsive pacing mode at a lower rate of about 40 beats/min) and pacing-guided phase, during which β-blocker dosage was titrated with a target of achieving >90% AAIR pacing (lower rate 60 beats/min). Sixty-one patients (64.2 ± 8.3 years old) were included. During the pacing-guided phase the target of ≥90% AAIR pacing was achieved in 80.3% of patients. Mean metoprolol dose during the clinically guided phase was 96.7 ± 29.4 versus 127.0 ± 39.6 mg/day in the pacing-guided phase (p <0.001). Appropriate ICD therapies were recorded in 35 patients (57.4%) during the clinically guided phase versus 20 (32.8%) during the pacing-guided phase (p <0.001; 1.15 and 0.48 appropriate ICD therapies per patient, respectively, p <0.001). In multivariate analysis, AAIR pacing and β-blocker dose were inversely related to appropriate ICD therapies. In conclusion, a pacing-guided approach for maximizing β-blocker doses guided by maximizing AAIR pacing in patients with ICDs may be beneficial compared to the conventional strategy. This pacing-guided approach led to higher daily β-blocker doses, which were correlated to fewer appropriate ICD therapies.

Differential effect of biventricular and right ventricular DDD pacing on coronary flow reserve in patients with ischemic cardiomyopathy

CRT and Coronary Flow Reserve.

BACKGROUND

Cardiac resynchronization therapy (CRT) has become a mainstay in heart failure management. There are also indications that upgrading of existing pacemakers to CRT systems may be of benefit. The aim of this study was to assess the effect of biventricular (BiV), compared with right ventricular (RV), pacing, on coronary flow reserve (CFR), in patients with ischemic cardiomyopathy.

METHODS AND RESULTS

From our database of heart failure patients implanted with BiV pacemakers, 20 patients (10 responders and 10 non-responders to CRT) were randomly selected. Left anterior descending artery coronary flow reserve was measured invasively, under BiV and RV pacing, using intracoronary adenosine to induce hyperemia. In all the 20 patients, there was a significant difference in the pairwise comparison between CFR recorded during BiV and RV pacing (mean difference 0.15, 95% confidence interval 0.07-0.23, P = 0.001). When comparing responders to non-responders, there was a significant difference as to the effect of BiV, compared with RV, pacing on CFR: mean difference (BiV minus RV CFR) was 0.26 ± 0.06 (95% confidence interval 0.13-0.39; P = 0.002), while in non-responders the difference was 0.04 ± 0.03 (95% confidence interval -0.02 to 0.10; P = 0.168).

CONCLUSION

BiV pacing is overall associated to higher CFR, compared with RV DDD pacing. This difference is almost exclusively attributable to the beneficial effect of CRT on coronary flow reserve in CRT-responders. This effect may contribute to the beneficial action of resynchronization in the failing heart and can be viewed in the context of reports of the usefulness of upgrading RV pacemakers to CRT systems.

Comparison of muscle functional electrical stimulation to conventional bicycle exercise on endothelium and functional status indices in patients with heart failure

The aim of this prospective, open-label, cohort study was to compare the effect of muscle functional electrical stimulation (FES) on endothelial function to that of conventional bicycle training. Eligible patients were those with New York Heart Association class II or III heart failure symptoms and ejection fractions ≤ 0.35. Two physical conditioning programs were delivered: FES of the muscles of the lower limbs and bicycle training, each lasting for 6 weeks, with a 6-week washout period between them. Brachial artery flow-mediated dilation (FMD) and other parameters were assessed before and after FES and the bicycle training program. FES resulted in a significant improvement in FMD, which increased from 5.9 ± 0.5% to 7.7 ± 0.5% (95% confidence interval for the difference 1.5% to 2.3%, p < 0.001). Bicycle training also resulted in a substantial improvement of endothelial function. FMD increased from 6.2 ± 0.4% to 9.2 ± 0.4% (95% confidence interval for the difference 2.5% to 3.5%, p < 0.001). FES was associated with a 41% relative increase in FMD, compared to 57% with bicycle exercise (95% confidence interval for the difference between the relative changes 1.2% to 30.5%, p = 0.034). This resulted in attaining a significantly higher FMD value after bicycle training compared to FES (9.2 ± 0.4% vs 7.7 ± 0.5%, p < 0.001). In conclusion, the effect of muscle FES in patients with heart failure on endothelial function, although not equivalent to that of conventional exercise, is substantial. Muscle FES protocols may prove very useful in the treatment of patients with heart failure who cannot or will not adhere to conventional exercise programs.

Effect of radiographic contrast media on markers of complement activation and apoptosis in patients with chronic coronary artery disease undergoing coronary angiography

The effects of radiographic contrast media on markers of complement activation and apoptosis in patients with chronic coronary artery disease (CAD) are unknown. The purpose of this study was to assess the comparative effects of ionic high-osmolar and non-ionic iso-osmolar radiographic contrast media on plasma markers of complement activation and apoptosis in patients with chronic CAD undergoing coronary angiography. Forty-four patients undergoing coronary angiography for chronic CAD were randomly assigned to receive the ionic high-osmolar radiographic contrast agent diatrizoate (Group A), or the non-ionic iso-osmolar contrast agent iodixanol (Group B) during angiography. Complement component 5 (C5a) and apoptotic markers sFas and sFasL were measured just prior to angiography and 1 hour after completion of angiography. Comparison of mean pre- and post-angiography plasma marker levels showed significantly greater increases in plasma levels in Group A than in Group B of C5a (29.30 +/- 5.45 ng/ml for Group A and 0.47 +/- 0.70 ng/ml for Group B (p < 0.00001), sFas (2.36 +/- 1.63 ng/ml for Group A and 0.23 +/- 0.90 ng/ml for Group B (p < 0.00001) and sFasL (14.00 +/- 5.41 pg/ml for Group A and 0.01 +/- 1.00 pg/ml for Group B (p < 0.00001). The results suggest that in patients with chronic CAD, the use of ionic high-osmolar radiographic contrast media during coronary angiography is associated with a more robust inflammatory and apoptotic milieu than that associated with the use of non-ionic iso-osmolar radiographic contrast media.