The importance of ventricular septal morphology in the effectiveness of dual chamber pacing in hypertrophic obstructive cardiomyopathy

Echocardiographic Predictors of All-Cause Mortality in Patients with Hypertrophic Cardiomyopathy following Pacemaker Implantation

Objectives

To examine the association between the echocardiographic parameters measured as left atrial diameter (LAD) and left ventricular end-diastolic diameter (LVEDD) and long-term risk of all-cause mortality in adults with hypertrophic cardiomyopathy (HCM) following pacemaker implantation.

Methods

A total of 94 adult patients with HCM who underwent pacemaker implantation from November 2002 to June 2013 in our Arrhythmia Center for symptomatic bradycardia and did not receive an implantable cardiac defibrillator (ICD) or cardiac resynchronization therapy (CRT) during follow-up were retrospectively extracted.

Results

After careful examination of the medical records, we retrospectively evaluated the clinical characteristics of 74 patients with LAD records (58.1 ± 14.9 years) and 76 patients with LVEDD records (57.6 ± 15.2 years). Based on the receiver-operating characteristic (ROC) curve, the values of LAD = 44 mm and LVEDD = 43 mm were identified to predict the all-cause mortality. In the Kaplan–Meier survival, LAD ≥44 mm and LVEDD ≥43 mm were both significantly associated with all-cause mortality (log-rank test P < 0.05). Cox regression analysis indicated that LAD ≥44 mm (HR 3.580; 95% CI = 1.055–12.148; P=0.041) was an independent predictor of all-cause mortality, while LVEDD ≥43 mm was not significantly associated with all-cause mortality. LVOTO was also significantly associated with all-cause mortality (HR = 0.166; 95% CI = 0.036–0.771; P=0.022).

Conclusions

In HCM patients with pacemaker implantation, LAD ≥44 mm was an independent predictor of all-cause mortality.

Pacing for drug-refractory or drug-intolerant hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic disease with an autosomal-dominant inheritance for which negative inotropes are the most widely used initial therapies. Observational studies and small randomised trials have suggested symptomatic and functional benefits using pacing and several theories have been put forward to explain why. Pacing, although not the primary treatment for HCM, could be beneficial to patients with relative or absolute contraindications to surgery or alcohol ablation. Several randomised controlled trials comparing pacing to other therapeutic modalities have been conducted but no Cochrane-style systematic review has been done.

OBJECTIVES

To assess the effects of pacing in drug-refractory or drug-intolerant hypertrophic cardiomyopathy patients.

SEARCH METHODS

We searched the following on the 14/4/2010: CENTRAL (The Cochrane Library 2010, Issue 1), MEDLINE OVID (from 1950 onwards ), EMBASE OVID (from 1980 onwards ), Web of Science with Conference Proceedings (from 1970 onwards). No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials of either parallel or crossover design that assess the beneficial and harmful effects of pacing for hypertrophic cardiomyopathy were included. When crossover studies were identified, we considered data only from the first phase.

DATA COLLECTION AND ANALYSIS

Data from included studies were extracted onto a pre-formed data extraction paper by two authors independently. Data was then entered into Review Manager 5.1 for analysis. Risk of bias was assessed using the guidance provided in the Cochrane Handbook. For dichotomous data, relative risk was calculated; and for continuous data, the mean differences were calculated. Where appropriate data were available, meta-analysis was performed. Where meta-analysis was not possible, a narrative synthesis was written. A QUROUM flow chart was provided to show the flow of papers.

MAIN RESULTS

Five studies (reported in 10 papers) were identified. However, three of the five studies provided un-usable data. Thus the data from only two studies (reported in seven papers) with 105 participants were included for this review. There was insufficient data to compare results on all-cause mortality, cost effectiveness, exercise capacity, Quality of life and Peak O2 consumption.When comparing active pacing versus placebo pacing on exercise capacity, one study showed that exercise time decreased from (13.1 ± 4.4) minutes to (12.6 ± 4.3) minutes in the placebo group and increased from (12.1 ± 5.6) minutes to (12.9 ± 4.2) minutes in the treatment group (MD 0.30; 95% CI -1.54 to 2.14). Statistically significant data from the same study showed that left ventricular outflow tract obstruction decreased from (71 ± 32) mm Hg to (52 ± 34) mm Hg in the placebo group and from (70 ± 24) mm Hg to (33 ± 27) mm Hg in the active pacing group (MD -19.00; 95% CI -32.29 to -5.71). This study was also able to show that New York Heart Association (NYHA) functional class decreased from (2.5 ± 0.5) to (2.2 ± 0.6) in the inactive pacing group and decreased from (2.6 ± 0.5) to (1.7 ± 0.7) in the placebo group (MD -0.50; 95% CI -0.78 to -0.22).When comparing active pacing versus trancoronary ablation of septal hypertrophy (TASH), data from one study showed that NYHA functional class decreased from (3.2 ± 0.7) to (1.5 ± 0.5) in the TASH group and decreased from (3.0 ± 0.1) to (1.9 ± 0.6) in the pacemaker group. This study also showed that LV wall thickness remained unchanged in the active pacing group compared to reduction from (22 ± 4) mm to (17 ± 3) mm in the TASH group (MD 0.60; 95% CI -5.65 to 6.85) and that LV outflow tract obstruction decreased from (80 ± 35.5) mm Hg in the TASH group to (49.3 ± 37.7) mm Hg in the pacemaker group.

AUTHORS' CONCLUSIONS

Trials published to date lack information on clinically relevant end-points. Existing data is derived from small trials at high risk of bias, which concentrate on physiological measures. Their results are inconclusive. Further large and high quality trials with more appropriate outcomes are warranted.

Comparison of dual-chamber pacing with nonsurgical septal reduction effect in patients with hypertrophic obstructive cardiomyopathy

OBJECTIVES

The aim of the study was to compare the influence of dual-chamber pacing vs. nonsurgical septal reduction on hemodynamic and morphological parameters in patients with obstructive form of hypertrophic cardiomyopathy.

METHODS

Nineteen patients with dual-chamber pacing (group I) and 9 patients who underwent nonsurgical septal reduction (group II) were studied at baseline and after a 6-month follow-up. The changes of left ventricular outflow tract gradient and posterior wall thickness (as an index of left ventricular hypertrophy regression) were compared.

RESULTS

The baseline left ventricular outflow tract gradient was comparable between group I and group II (77+/-25 vs. 82+/-25 mm Hg, p>0.05). At 6-month follow-up, the left ventricular outflow tract gradient was reduced to a similar level in both groups (28+/-19 vs. 25+/-12 mm Hg, p>0.05). At baseline, posterior wall hypertrophy was comparable between groups (12.9+/-1.7 vs. 13.6+/-2.2 mm, p>0.05). During follow-up, the posterior wall thickness was unchanged in the pacing group (12.9+/-1.7 vs. 12.6+/-1.6 mm, p>0.05), whereas nonsurgical septal reduction induced regression of left ventricular hypertrophy in myocardial region remote from the infarcted septal segment (13.6+/-2.2 vs. 10.5+/-2.3 mm, p<0.003).

CONCLUSION

Despite comparable reduction of instantaneous left ventricular outflow tract gradient, the nonsurgical septal reduction decreased posterior wall thickness, whereas pacing did not reduce left ventricular hypertrophy. Thus, regression of left ventricular hypertrophy that appeared solely after nonsurgical septal reduction may reflect the more permanent reduction of left ventricular pressure overload. Thus, not only hemodynamic but also morphological benefit from nonsurgical septal reduction seems to indicate the superiority of this method over dual-chamber pacing.