Dual-chamber pacing for hypertrophic cardiomyopathy: a randomized, double-blind, crossover trial

New trends in treatment of hypertrophic cardiomyopathy

The management of patients with hypertrophic cardiomyopathy (HCM) has evolved markedly over the past 20 years, particularly with the rising number of indications for implantable cardiac defibrillators (ICDs) and alcohol septal ablation (ASA). However, medical therapies targeted to improve quality of life are underused; when resting and/or exercise obstruction is present, an incremental and additive approach should be used based on a high dosage of beta-blockers, verapamil and/or disopyramide. Radiofrequency catheter ablation of atrial fibrillation or A-V node has been proposed in some instances. Treatment of syncope or presyncope due to an abnormal blood pressure response during exercise remains challenging. Only patients with obstruction who remain severely symptomatic despite maximal medical therapy should be considered for invasive procedures, including dual-chamber (DDD) pacing, ASA or surgery. The reported complication rates of ASA (essentially complete A-V block, incidence above 5-10%, with mortality rates ranging from 0-4%) and the benefits at medium-term follow-up appear comparable to those observed after myectomy, which, according to guidelines, should remain the primary treatment for most severely symptomatic drug-refractory young patients with obstruction. While the overall survival of patients with HCM is similar to that of the general population, detection of patients at high risk of sudden cardiac death remains challenging, particularly in the young, and indications for ICDs in high risk patients without prior cardiac arrest should be patient- and family-orientated.

Surgical management of obstructive hypertrophic cardiomyopathy: the gold standard

While medication is the first line of therapy in obstructive hypertrophic cardiomyopathy, patients who have symptoms refractory to medical treatment or asymptomatic patients with high resting gradients (>or=30 mmHg) may require septal myectomy. Surgical septal myectomy can be performed safely, with excellent survival, relief from symptoms and low morbidity. Alcohol septal ablation is an alternative to surgical treatment, but late outcomes are uncertain. Although both methods of septal reduction relieve left ventricular outflow tract gradients and improve functional status, the need for permanent pacing appears higher with alcohol ablation compared with surgical myectomy. As our understanding of obstructive hypertrophic cardiomyopathy continues to grow, the indications for intervention will evolve. In our practice, septal myectomy remains the gold standard for treatment of obstructive hypertrophic cardiomyopathy.

Canadian Cardiovascular Society Consensus Conference guidelines on heart failure--2008 update: best practices for the transition of care of heart failure patients, and the recognition, investigation and treatment of cardiomyopathies

Heart failure is a clinical syndrome that normally requires health care to be provided by both specialists and nonspecialists. This is advantageous because patients benefit from complementary skill sets and experience, but can present challenges in the development of a common, shared treatment plan. The Canadian Cardiovascular Society published a comprehensive set of recommendations on the diagnosis and management of heart failure in January 2006, and on the prevention, management during intercurrent illness or acute decompensation, and use of biomarkers in January 2007. The present update builds on those core recommendations. Based on feedback obtained through a national program of heart failure workshops during 2006 and 2007, several topics were identified as priorities because of the challenges they pose to health care professionals. New evidence-based recommendations were developed using the structured approach for the review and assessment of evidence that was adopted and previously described by the Society. Specific recommendations and practical tips were written for best practices during the transition of care of heart failure patients, and the recognition, investigation and treatment of some specific cardiomyopathies. Specific clinical questions that are addressed include: What information should a referring physician provide for a specialist consultation? What instructions should a consultant provide to the referring physician? What processes should be in place to ensure that the expectations and needs of each physician are met? When a cardiomyopathy is suspected, how can it be recognized, how should it be investigated and diagnosed, how should it be treated, when should the patient be referred, and what special tests are available to assist in the diagnosis and treatment? The goals of the present update are to translate best evidence into practice, apply clinical wisdom where evidence for specific strategies is weaker, and aid physicians and other health care providers to optimally treat heart failure patients, resulting in a measurable impact on patient health and clinical outcomes in Canada.

Surgery Insight: septal myectomy for obstructive hypertrophic cardiomyopathy—the Mayo Clinic experience

Septal myectomy has been the gold standard treatment for the relief left ventricular outflow tract obstruction and cardiac symptoms in both adults and children with obstructive hypertrophic cardiomyopathy. In almost all circumstances, abnormalities of the mitral valve and subvalvar mitral apparatus can be managed without the need for mitral valve replacement, and other cardiac lesions can be repaired simultaneously. In the current era, the operative mortality for isolated septal myectomy at an experienced center is low in both children and adults (approximately 1%). Excellent late results with myectomy are gratifying: 90% of patients improve by at least one NYHA class, and improvements persist in most individuals on late follow-up. Late survival in patients with obstructive hypertrophic cardiomyopathy who undergo myectomy exceeds that of patients who do not receive surgical treatment and, in addition, myectomy may be associated with reduced long-term risk of sudden cardiac death. These results should serve as a basis for comparison with newer nonsurgical treatment regimens.

Resynchronization or dyssynchronization--successful treatment with biventricular stimulation of a child with obstructive hypertrophic cardiomyopathy without dyssynchrony

We present a case of a 10-year-old boy with hypertrophic cardiomyopathy, intraventricular pressure gradient of 104 mmHg, and indications for prophylactic ICD implantation. Based on intraoperative pressure measurements, the child was implanted with biventricular ICD. During 2.5 months of observation, the patient's functional status improved significantly, as shown by subjective and objective parameters and, moreover, the pressure gradient fell to 12 mmHg. Significant electrical and mechanical cardiac dyssynchrony appeared parallel to clinical improvement.

Placebo and nocebo in cardiovascular health: implications for healthcare, research, and the doctor-patient relationship

Despite treatments proven effective by sound study designs and robust end points, placebos remain integral to elicit effective medical care. The authenticity of the placebo response has been questioned, but placebos likely affect pain, functionality, symptoms, and quality of life. In cardiology, placebos influence disability, syncope, heart failure, atrial fibrillation, angina, and survival. Placebos vary in strength and efficacy. Compliance to placebo affects outcomes. Nocebo responses can explain some adverse clinical outcomes. A doctor may be an unwitting contributor to placebo and nocebo responses. Placebo and nocebo mechanisms, not well understood, are likely multifaceted. Placebo and nocebo use is common in practice. A successful doctor-patient relationship can foster a strong placebo response while mitigating any nocebo response. The beneficial effects of placebo, generally undervalued, hard to identify, often unrecognized, but frequently used, help define our profession. The role of the doctor in healing, above the therapy delivered, is immeasurable but powerful. An effective placebo response will lead to happy and healthy patients. Imagine instead the future of healthcare relegated to a series of guidelines, tests, algorithms, procedures, and drugs without the human touch. Healthcare, rendered by a faceless, uncaring army of protocol aficionados, will miss an opportunity to deliver an effective placebo response. Wise placebo use can benefit patients and strengthen the medical profession.

Pathophysiology and Treatment of Hypertrophic Cardiomyopathy

All patients with hypertrophic cardiomyopathy (HCM) should have five aspects of care addressed. An attempt should be made to detect the presence or absence of risk factors for sudden arrhythmic death. If the patient appears to be at high risk, discussion of the benefits and risks of ICD are indicated, and many such patients will be implanted. Symptoms are appraised and treated. Bacterial endocarditis prophylaxis is recommended. Patients are advised to avoid athletic competition and extremes of physical exertion. First degree family members should be screened with echocardiography and ECG.

Long-term effects of dual-chamber pacing with periodic echocardiographic evaluation of optimal atrioventricular delay in patients with hypertrophic cardiomyopathy >50 years of age

Various treatment modalities have been introduced to reduce the subaortic pressure gradient in patients with obstructive hypertrophic cardiomyopathy, including pacemaker insertion. Complete ventricular capture during pacing is essential and requires optimization of the atrioventricular interval (AVI). In this study, a protocol using echocardiographic examination assessing the changes in the left ventricular outflow tract (LVOT) gradient in different AVIs, pacing rates, and pacing modes was used for optimal pacemaker programming. Twenty-five patients with obstructive hypertrophic cardiomyopathy were implanted with DDD pacemakers and evaluated prospectively. The LVOT gradient was measured during periodic evaluations every 3 to 6 months. Gradient measurements were done with 5 different AVIs and 3 different rate combinations. After each evaluation, the optimal AVI, pacing rate, and mode were set on the basis of the minimal LVOT gradient not associated with systolic arterial cuff pressure reduction. Follow-up ranged from 18 to 126 months. Peak LVOT gradient immediately decreased in 92% of patients. During follow-up, the optimal AVI was prolonged in most patients. Sixty-four percent of patients showed a clear relation between pacemaker modifications and gradient reduction. In 75% of these patients, optimal gradient reduction required repeated AVI and pacing rate programming on the basis of echocardiographic evaluation. Symptoms decreased in 92% of patients, and New York Heart Association class improved significantly (3.1+/-0.7 vs 1.3+/-0.4, p<0.001) during follow-up. The symptomatic reduction was positively correlated with the LVOT gradient reduction. In conclusion, DDD pacing is effective in reducing the LVOT gradient and improving functional capacity in adult patients with hypertrophic cardiomyopathy. Pacemaker programming with the periodic echocardiographic evaluation of the optimal AVI, pacing rate, and mode is imperative for optimal results.

Percutaneous septal ablation for left mid-ventricular obstructive hypertrophic cardiomyopathy: a case report

BACKGROUND

Mid-ventricular obstructive hypertrophic cardiomyopathy (MVOHC) is a rare type of cardiomyopathy. The diagnosis is based on the hourglass appearance on the left ventriculogram and the presence of pressure gradient between apical and basal chamber of the ventriculum on the hemodynamic assessment.

CASE PRESENTATION

The present case represents successful percutaneous treatment with septal ablation to patient with MVOHC associated with systolic anterior motion of the mitral valve and obstruction at both the mid-ventricular and outflow levels.

CONCLUSION

Alcohol septal ablation has been proposed as less invasive alternatives to surgery in patients with MVOHC.

Pacemaker-induced mitral regurgitation as a cause of refractory congestive heart failure during pacing therapy in a patient with hypertrophic obstructive cardiomyopathy

This report describes a woman with hypertrophic obstructive cardiomyopathy in whom initial hemodynamic improvement by dual chamber (DDD) pacing with short atrioventricular delay was excellent, but severe mitral regurgitation developed during the subsequent follow-up period, resulting in refractory congestive heart failure. There were two possible explanations for the origin of the complicating mitral regurgitation in this patient: pacing-induced semiclosure of the mitral valve, or left ventricular asynchrony caused by right ventricular pacing. Heart failure in patients with hypertrophic obstructive cardiomyopathy who undergo placement of a DDD pacemaker to improve not only mitral regurgitation but also heart failure symptoms can be associated with systolic mitral regurgitation as the cause of failure in DDD pacing therapy.

Percutaneous myocardial ablation for left mid-ventricular obstructive hypertrophic cardiomyopathy

Mid-ventricular obstructive hypertrophic cardiomyopathy (MVOHC) is a rare type of cardiomyopathy. The diagnosis is based on the hourglass appearance on the left ventriculogram and the presence of pressure gradient between apical and basal chamber of the ventriculum on the hemodynamic assessment. Atrio-ventricular sequential pacing and alcohol ablation have been proposed as less invasive alternatives to surgery for patients who fail to respond to pharmacologic therapy. The present case represents successful percutaneous treatment with alcohol ablation to patient with MVOHC and apical aneurysm. Alcohol ablation to distal segment of the left anterior descending artery resulted with relief of clinical symptoms and intra-ventricular pressure gradient.

Usefulness of tissue Doppler imaging for demonstrating altered septal contraction sequence during dual-chamber pacing in obstructive hypertrophic cardiomyopathy

Dual-chamber pacing reduces left ventricular (LV) outflow obstruction in patients with obstructive hypertrophic cardiomyopathy (HC), the mechanism of which lies in pacing-induced paradoxic septal motion. This study was conducted to test the hypothesis that tissue Doppler imaging (TDI) could demonstrate changes in the septal contraction sequence during dual-chamber pacing in patients with HC. TDI was performed in 16 patients (5 women; mean age 63+/-11 years) who underwent dual-chamber pacing for 7.6+/-2.1 year. With and without pacing, the time to peak systolic myocardial velocity was measured from the basal, mid, and distal segments in the 4 different LV walls. Without pacing, there was almost no longitudinal segmental asynchrony. During pacing, however, marked longitudinal segmental asynchrony appeared, especially in the anteroseptal wall (from p=NS to p<0.01 by analysis of variance) and the ventricular septum (from p<0.05 to p<0.01), with the time to peak velocity extremely prolonged at the distal segments. This was associated with a modest but significant decrease in the LV pressure gradient (from 20+/-8 to 14+/-7 mm Hg, p<0.01). In patients with obstructive HC, altered septal contraction sequence accounts for the reduced LV outflow obstruction during dual-chamber pacing, which was clearly demonstrated by TDI.

Intracardiac echocardiography guidance during percutaneous transluminal septal myocardial ablation in patients with obstructive hypertrophic cardiomyopathy

BACKGROUND

Percutaneous transluminal septal myocardial ablation (PTSMA) recently emerged as an alternative to myectomy for hypertrophic obstructive cardiomyopathy (HOCM) patients with drug-refractory symptoms. The target septal branch selection is a main point to achieve the therapeutic result.

METHODS AND RESULTS

We report about PTSMA performed using intracardiac echocardiography (ICE) to guide the procedure in 9 symptomatic HOCM patients. The target septal branch was chosen on the basis of the risk-area visualized using ICE after injection of a contrast agent. During alcohol administration a backscattered signal enhancement of the infarcted area was detected. The procedures were uncomplicated and effective to reduce the gradient from 78.9+/-20.4 mmHg to 7.8+/-7.9 mmHg (p<0.0001).

CONCLUSIONS

In this initial experience ICE monitoring during PTSMA was safe and provided high quality and continuous imaging of the treated segment of the septum during the whole procedure.

A prospective follow-up of alcohol septal ablation for symptomatic hypertrophic obstructive cardiomyopathy--the Baylor experience (1996-2002)

BACKGROUND

There is a paucity of data on the long-term outcome of alcohol septal ablation (ASA) for symptomatic hypertrophic obstructive cardiomyopathy (HOCM).

HYPOTHESIS

The study was undertaken to evaluate the longer-term outcome of ASA therapy for symptomatic HOCM.

METHODS

In all, 137 patients were enrolled consecutively (1996-1999) and 130 (95%) (74 men, 56 women, aged 51 +/- 17 years) underwent ASA and had serial prospective follow-up for up to 5 years (mean follow-up 3.6 +/- 1.4 years). Evaluation included angina (Canadian Cardiovascular Society [CCS] score), dyspnea (New York Heart Association [NYHA] class), duration of exercise on treadmill, and echocardiographic indices.

RESULTS

Ethanol (3.5 +/- 1.5 cc), injected into 1.5 +/- 0.6 arteries, induced a mean peak plasma creatine kinase (CK) of 1676 +/- 944 units. Complications of procedures included death 1.5% (2/130), heart block requiring permanent pacemaker 13% (17/130), and coronary dissection 4.4% (6/130). Baseline versus last follow-up visit: NYHA class decreased from 3.0 +/- 0.4 to 1.2 +/- 0.6 (p < 0.01); CCS angina score from 2.0 +/- 0.8 to 0.08 +/- 0.4 (p < 0.01); and duration of exercise increased from 322 +/- 207 to 443 +/- 200 s (p < 0.01). Resting left ventricular outflow tract gradient at baseline versus last follow-up visit showed a decrease from 74 +/- 30 to 4 +/- 13 (p < 0.01), and the dobutamine-provoked gradient of 88 +/- 29 decreased to 21 +/- 21 (p < 0.01) mmHg. All-cause mortality over the duration of follow-up was 7.7% (10) giving an annual rate of 2.1%, and cardiac mortality was 2.3% (3) reflecting an annual rate of 0.6%.

CONCLUSIONS

Alcohol septal ablation decreased symptoms and improved exercise performance, indicating that it is an effective procedure for symptomatic HOCM.

Impact of Right Atrial-Left Ventricular Dual-Chamber Permanent Pacing in Patients With Severely Symptomatic Hypertrophic Obstructive Cardiomyopathy

BACKGROUND

Effective alternatives to surgical myectomy for patients with symptomatic hypertrophic obstructive cardiomyopathy (HOCM) remain unestablished. Dual-chamber (DDD) pacing was evaluated in these patients using right atrial (RA) and epicardial left ventricular (LV) leads.

METHODS AND RESULTS

In 6 patients with HOCM refractory to medical therapy and conventional RA-right ventricular (RV) DDD pacing, we implanted DDD pacemakers using RA and epicardial LV leads. The baseline intraventricular pressure gradient before pacemaker implantation was 103+/-44 mmHg. The pressure gradient decreased significantly to 8+/-16 mmHg by temporary RA-LV DDD pacing (p=0.006), while it decreased only to 68+/-25 mmHg by temporary RA-RV pacing (NS). It was nearly eliminated to 1+/-2 mmHg (p=0.027) 3 months after RA-LV DDD pacemaker implantation. LV end-diastolic pressure, cardiac index and systolic aortic pressure did not change significantly. New York Heart Association class improved in all patients (p=0.023). Brain and atrial natriuretic peptide concentrations, respectively 516+/-286 and 143+/-34 pg/ml at baseline, decreased significantly to 230+/-151 and 93+/-44 pg/ml 3 months after implantation (p=0.027 and 0.028).

CONCLUSION

RA-LV DDD pacemaker implantation is a useful option for patients with symptomatic HOCM.

The case for surgery in obstructive hypertrophic cardiomyopathy

Relief of left ventricular (LV) outflow obstruction in patients with hypertrophic cardiomyopathy (HCM) and disabling symptoms refractory to maximum medical management has historically been a surgical problem. Surgical septal myectomy permanently abolishes systolic anterior motion of the mitral valve and mitral regurgitation, while normalizing LV pressures and wall stress. Also, these salutary goals are achieved without encumbering patients with post-procedural devices (e.g., pacemakers or defibrillators) or creating potentially arrhythmogenic substrates, as may occur with alcohol septal ablation. Procedural morbidity and mortality risk with myectomy is similar to, and in some institutions less than those for alcohol septal ablation. Over four decades, reports from numerous centers worldwide have consistently and unequivocably documented the benefits of surgery on hemodynamic and functional state, restoring normal and acceptable quality of life to patients of all ages by largely reversing the complications of heart failure. Long-term survival after myectomy is similar to that of the general population and superior to non-operated patients with obstruction. The LV outflow tract morphology in HCM is heterogeneous and not uncommonly includes congenital anomalies of the mitral valve apparatus for which the surgeon has the flexibility to adapt the repair, often employing an extended myectomy. In the current atmosphere of increasing and perhaps excessive enthusiasm for newer catheter-based interventions, it is a critical time to promote and re-emphasize that surgery is the time-honored (and presently the most effective) treatment strategy for relieving heart failure-related disability resulting from dynamic LV outflow obstruction in HCM, and is the primary treatment option for this subgroup of severely symptomatic drug-refractory patients.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is a primary disorder of the myocardium characterised by disproportionate hypertrophy of the ventricular wall. It is the most common genetic cardiac disease with an incidence of 1 in 500 and it is diagnosed most commonly using transthoracic echocardiography. This review article discusses: the diagnosis of hypertrophic cardiomyopathy; the differential diagnoses; the characteristic histological signs found at postmortem and/or myectomy and the clinical symptoms and signs. Current recommendations for myectomy of first degree relatives, based on the ACC/ESC guidelines, are discussed as well as general management and then specific management for various subgroups and symptomatic patients.

Cardiac pacing: the state of the art

Permanent cardiac pacing remains the only effective treatment for chronic, symptomatic bradycardia. In recent years, the role of implantable pacing devices has expanded substantially. At the beginning of the 21st century, exciting developments in technology seem to happen at an exponential rate. Major advances have extended the use of pacing beyond the arrhythmia horizon. Such developments include dual-chamber pacers, rate-response algorithms, improved functionality of implantable cardioverter defibrillators, combinations of sensors for optimum physiological response, and advances in lead placement and extraction. Cardiac pacing is poised to help millions of patients worldwide to live better electrically. We review pacing studies of sick-sinus syndrome, neurocardiogenic syncope, hypertrophic obstructive cardiomyopathy, and cardiac resynchronisation therapy, which are common or controversial indications for cardiac pacing. We also look at the benefits and complications of implantation in specific arrhythmias, suitability of different pacing modes, and the role of permanent pacing in the management of patients with heart failure.

Intra- and interatrial conduction delay: implications for cardiac pacing

Atrial conduction disorders are frequent in elderly subjects and/or those with structural heart diseases, mainly mitral valve disease, hyperthrophic cardiomyopathies, and hypertension. The resultant electrophysiological and electromechanical abnormalities are associated with a higher risk of paroxysmal or persistent atrial tachyarrhythmias, either atrial fibrillation, typical or atypical flutter or other forms of atrial tachycardias. Such an association is not fortuitous because intra- and interatrial conduction abnormalities delays disrupt (spatial and temporal dispersion) electrical activation, thus promoting the initiation and perpetuation of reentrant circuits. Preventive therapeutic interventions induce variable, sometimes paradoxical effects as with the proarrhythmic effect of class I antiarrhythmic drugs. Similarly, atrial pacing may promote proarrhythmias or an antiarrhythmic effect according to the pacing site(s) and mode. Multisite atrial pacing was conceived to correct, as much as possible, abnormal activation induced by spontaneous intra- or interatrial conduction disorders or by single site atrial pacing, which are situations responsible for commonly refractory arrhythmias. Atrial electrical resynchronization can also be used to correct mechanical abnormalities like left heart AV dyssynchrony resulting from intraatrial conduction delays.

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is a common genetically transmitted disease, defined clinically by the presence of unexplained left ventricular hypertrophy. The disease has a varied clinical course and outcome; many patients have little or no discernible cardiovascular symptoms, whereas others have profound exercise limitation and recurrent arrhythmias. The overall risk of disease-related complications such as sudden death, endstage heart failure, and fatal stroke is roughly 1-2% per year, but the absolute risk in individuals varies as a function of underlying genetic abnormality, age, myocardial pathology, and other pathophysiological abnormalities such as impaired peripheral vascular responses. Genetic counselling and clinical risk stratification are relevant to all patients, but many therapeutic interventions, including septal alcohol ablation, septal myectomy, and implantable cardioverter defibrillators, are appropriate only in particular patient subsets. We review the management of patients with unexplained myocardial hypertrophy, considering the influence of underlying genetic and pathophysiological substrates on clinical decision-making.

Dual chamber versus single chamber ventricular pacemakers for sick sinus syndrome and atrioventricular block

BACKGROUND

Dual chamber pacing or single chamber atrial pacing ('physiologic' pacing) is believed to have an advantage over single chamber ventricular pacing in that it resembles cardiac physiology more closely by maintaining atrioventricular (AV) synchrony and dominance of the sinus node, which in turn may reduce cardiovascular morbidity and mortality thus contributing to patient survival and quality of life. However, a significant proportion of pacemakers currently implanted are single chamber ventricular pacemakers.

OBJECTIVES

The objective of this review was to assess the short- and long-term clinical effectiveness of dual chamber pacemakers compared to single chamber ventricular pacemakers in adults with AV block, sick sinus syndrome or both. An additional objective was to assess separately any potential differences in effectiveness between dual chamber pacing and single chamber atrial pacing. The clinical effectiveness of single chamber atrial pacing versus single chamber ventricular pacing was not examined.

SEARCH STRATEGY

The Cochrane Controlled Trials Register (The Cochrane Library Issue 3, 2002), MEDLINE (1966 to 2002), EMBASE (1980 to 2002) and the Science Citation Index (1980 to 2002) were searched on 19th August 2002. Citation lists and web sites were checked and researchers in the field contacted.

SELECTION CRITERIA

Parallel group or crossover randomised controlled trials of at least 48 hours duration comparing dual chamber pacing and single chamber ventricular pacing, and investigating cardiovascular morbidity, mortality, patient related quality of life, exercise capacity and complication rates.

DATA COLLECTION AND ANALYSIS

Data was extracted onto pre-piloted data extraction forms. Quality assessment was undertaken using a checklist, with a sub-sample of quality data independently extracted by a second reviewer. Where appropriate data was available, meta-analysis was performed. Where meta-analysis was not possible, the number of studies showing a positive, neutral or negative direction of effect and statistical significance were simply counted.

MAIN RESULTS

Five parallel and 26 crossover randomised controlled trials were identified. The quality of reporting was found to be poor. Pooled data from parallel studies shows a statistically non-significant preference for physiologic pacing (primarily dual chamber pacing) for the prevention of stroke, heart failure and mortality, and a statistically significant beneficial effect regarding the prevention of atrial fibrillation (odds ratio (OR) 0.79, 95% CI 0.68 to 0.93). Both parallel and crossover studies favour dual chamber pacing with regard to pacemaker syndrome (parallel: Peto OR 0.11, 95% CI 0.08 to 0.14; crossover: standardised mean difference (SMD) -0.74, 95% CI - 0.95 to -0.52). Pooled data from crossover studies shows a statistically significant trend towards dual chamber pacing being more favourable in terms of exercise capacity (SMD -0.24, 95% CI -0.03 to -0.45). No individual studies reported a significantly more favourable outcome with single chamber ventricular pacing.

REVIEWERS' CONCLUSIONS

This review shows a trend towards greater effectiveness with dual chamber pacing compared to single chamber ventricular pacing, which supports the current British Pacing and Electrophysiology Group's Guidelines regarding atrioventricular block. Additional randomised controlled trial evidence from ongoing trials in this area will further inform the debate.

Difficult cases in heart failure. Percutaneous transluminal septal myocardial ablation in the management of hypertrophic obstructive cardiomyopathy

Hypertrophic cardiomyopathy is a complex genetic condition with a heterogeneous clinical course. Some patients remain asymptomatic throughout life while others develop one or more of the adverse clinical consequences including symptoms of congestive heart failure with exertional dyspnea and functional disability (usually with preserved left ventricular systolic function), atrial fibrillation, or sudden cardiac death. Because of this heterogenicity in the clinical presentations, management of patients with hypertrophic cardiomyopathy includes a wide range of pharmacologic therapies as well as invasive approaches. In recent years, nonsurgical catheter-based treatment of hypertrophic cardiomyopathy has been increasingly used in the management of a subset of these patients. The authors present a case of percutaneous transluminal septal myocardial ablation in a patient with hypertrophic cardiomyopathy who was symptomatic despite maximal medical treatment.

Hypertrophic cardiomyopathy: state-of-the-art review, with focus on the management of outflow obstruction

Significant advances in our understanding and management of hypertrophic cardiomyopathy have been made in the last decade, as the complex genetics and phenotype-genotype correlations that characterize the disease are gradually unravelled. The well-described clinical heterogeneity of hypertrophic cardiomyopathy is now understood to be based on profound genetic variability, with at least 10 genes and over 150 mutations implicated. Several new therapeutic tools have entered clinical practice. The implantable cardioverter-defibrillator is now strongly indicated in those at high risk of sudden arrhythmic death. Our ability to abort sudden death in this subgroup has placed added emphasis on risk stratification in newly diagnosed patients. New procedures have also been developed for the relief of outflow obstruction in patients with refractory symptoms and a significant subaortic outflow gradient. Although not as efficacious as the 'gold-standard' surgical myectomy-myotomy, dual-chamber pacemaker implantation can be of modest benefit in select patients. Percutaneous transluminal septal myocardial ablation is an emerging catheter-based procedure for the relief of left ventricular outflow obstruction. Long-term follow-up data are still awaited. However, intermediate-term results suggest equivalent efficacy to surgical myectomy-myotomy.

Evidence for anti-ischemic effect of dual-chamber pacing in patients with the obstructive form of hypertrophic cardiomyopathy

Dual-chamber pacing reportedly improves the quality of life by reducing the frequency of anginal episodes in selected patients with the obstructive form of hypertrophic cardiomyopathy (HCM), although the underlying mechanism or coronary effect is poorly understood. We report 3 patients with obstructive HCM, in whom the effects of atrial vs. dual-chamber tachypacing on systemic hemodynamics and myocardial lactate metabolism were studied. In all patients myocardial lactate production, objective evidence of myocardial ischemia, was demonstrated during atrial pacing, whereas no patient developed myocardial ischemia during dual-chamber pacing. By contrast, the responses of pressure gradient to pacing varied among the patients. These observations demonstrate for the first time that dual-chamber pacing exerted an anti-ischemic effect in obstructive HCM, which may contribute, at least partly, to the beneficial effects of chronic AV pacing on angina status and/or LV function.

The efficacy of cibenzoline for reducing the left ventricular pressure gradient of hypertrophic obstructive cardiomyopathy: A case report

A 46 year-old man with hypertrophic obstructive cardiomyopathy (HOCM) was referred to this clinic complaining of shortness of breath. His symptoms remained even after he had been treated with bisoprolol, lisinopril, and verapamil. We started treating him with cibenzoline, instead of verapamil. Continuous-wave Doppler examination revealed a marked decrease from 95.9 mm Hg to 8.8 mmHg in the left ventricular outflow tract pressure gradient after administration of cibenzoline, and the symptom disappeared. The electrical axis of the electrocardiogram deviated from +53 to +95 degrees, and the QRS interval was increased from 0.095 to 0.114 seconds. By the M-mode echocardiogram, the interventricular septum was observed moved paradoxically in the early, systolic phase. We suggest the possibility that cibenzoline modifies intraventricular conduction and causes asynchronous contraction of the left ventricle, resulting in decrease in the left ventricular outflow tract pressure gradient.

Remodelado ventricular izquierdo tras ablación septal percutánea con alcohol en pacientes con miocardiopatía hipertrófica obstructiva: estudio ecocardiográfico

INTRODUCTION

In patients with hypertrophic obstructive cardiomyopathy, obstruction in the left ventricular outflow tract may generate more hypertrophy. Our aim was to evaluate the impact of reducing ventricular outflow tract obstruction on left ventricular hypertrophy and remodeling after alcohol septal ablation.

PATIENTS AND METHOD

20 patients with hypertrophic obstructive cardiomyopathy who underwent alcohol septal ablation were included. Doppler echocardiography was performed in all patients at baseline, immediately after alcohol septal ablation, and at 3 and 12 months' follow-up. Left ventricular diameters and wall thickness and pressure gradients in the ventricular outflow tract were determined.

RESULTS

Immediately after alcohol septal ablation, ventricular outflow tract pressure gradient decreased from 63.0 27.7 to 28.2 24.7 mmHg (p < 0.001), without significant changes in left ventricular dimensions. However, after 12 months we observed an increase in left ventricular end-diastolic (from 47.1 4.9 to 50.8 4.5 mm) and end-systolic diameter (from 27.1 3.0 to 33.7 4.6 mm), as well as a reduction in septal (from 19.5 4.0 to 15.5 2.7 mm) and posterior wall thickness (from 14.0 2.2 to 12.9 1.3 mm) (p < 0.01 in all cases). Left ventricular end-diastolic and end-systolic volumes increased (from 106.4 26.9 to 123.1 28.7 ml and from 50.2 17.3 to 56.7 18.3 ml, respectively, p < 0.01 in both cases), without changes in left ventricular ejection fraction. The reduction in ventricular outflow tract pressure gradient at 12 months' follow-up correlated significantly with the increase in left ventricular end-systolic diameter (r = 0.63; p < 0.01).

CONCLUSIONS

In patients with hypertrophic obstructive cardiomyopathy who underwent alcohol septal ablation, relief of ventricular outflow tract obstruction is associated with an increase in left ventricular chamber diameters and volume. These findings suggest that middle- and long-term ventricular remodeling and regression of hypertrophy occur in these patients, which may contribute to their clinical improvement.

Hypertrophic Cardiomyopathy

When an individual is diagnosed with hypertrophic cardiomyopathy (HCM), all relatives potentially affected by Mendelian autosomal-dominant inheritance should be evaluated with an electrocardiogram (ECG) and echocardiogram. Genetic testing should be considered in high-risk mutations where there are diagnostic uncertainties. Symptom relief depends on beta-blockers as first-line therapy. If the disease is nonobstructive, then calcium channel blockers can be added or used alone. If there is a significant left ventricular outflow tract (LVOT) gradient then disopyramide can be used, ideally in combination with a beta-blocker. Verapamil should be used with care due to potential exacerbation of the LVOT gradient. Nonmedical therapy for obstructive disease consists of surgical myectomy, alcohol septal ablation, or dual-chamber pacing. Surgery is the gold standard, although in experienced hands and directed appropriately, septal ablation achieves good results. Pacing is generally less effective. The development of atrial fibrillation (AF) or left atrial enlargement carries a significant risk of thromboembolism. All patients should be closely observed for AF and thromboembolic risk, and the threshold for initiation of anticoagulation should be low in patients with sustained palpitations, atrial enlargement, and nonsustained supraventricular arrhythmia on Holter. All patients with HCM should be assessed for their risk of sudden death regardless of severity of symptoms or morphology. The factors predictive of risk are 1) previous cardiac arrest; 2) unexplained syncope; 3) family history of premature sudden death; 4) abnormal blood pressure response to exercise; 5) nonsustained ventricular tachycardia; and 6) severe left ventricular hypertrophy >/= 30 mm.

Echocardiographic assessment of patients with hypertrophic and restrictive cardiomyopathy: imaging and echocardiography

Echocardiography has evolved to be an important tool in the assessment of patients with hypertrophic and restrictive cardiomyopathy. In this article, the authors review the use of echocardiography in diagnosis, differentiation from disease mimics, assessment of prognosis, and the assistance of specific therapies. A pathophysiologic understanding of restrictive cardiomyopathy and constrictive pericarditis will be reviewed along with echocardiographic and Doppler features that help to distinguish these two entities.