Profound "pacemaker syndrome" in hypertrophic cardiomyopathy

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.

Pacing in hypertrophic cardiomyopathy

Dual chamber pacing has been proposed as an alternative to surgery in the management of hypertrophic cardiomyopathy. Reports have documented hemodynamic and symptomatic benefit from dual chamber pacing, raising the question of whether or not all patients with drug-refractory symptoms should undergo a trial of pacing before consideration of surgery. The enthusiasm for pacing in hypertrophic cardiomyopathy has generated a number of investigations addressing this issue, including several recently concluded clinical trials. This article reviews the recent experience with dual chamber pacing in hypertrophic cardiomyopathy.

Dual chamber pacing in hypertrophic obstructive cardiomyopathy: beneficial effect of atrioventricular junction ablation for optimal left ventricular capture and filling

Clinical improvement with dual chamber pacing has largely been reported in patients suffering from hypertrophic obstructive cardiomyopathy and mainly attributed to the reduction of the subaortic pressure gradient. To be effective, pacing must induce a permanent and complete capture of the LV. In two patients of our collective, symptoms (angina and dyspnea NYHA Class III and/or syncopes) persisted or relapsed despite pacing. This was related to the inability to obtain full LV capture due to a too-short native PR interval. RF ablation of the AV junction was therefore performed in both patients, resulting in permanent AV block in one and prolonged PR interval up 310 ms in the second. Pacing was thereafter associated with an immediate and significant clinical improvement related to permanent LV capture, whatever the patient's activity. After RF ablation, the AV delay was set up to induce the best LV filling, as assessed by Doppler analysis of mitral flow. Our observations suggest that RF ablation or modification of the AV junction can be a successful procedure in some patients with residual or recurrent symptoms, when the latter result from a loss of capture or from the inability to program an AV delay that does not compromise the active component to LV filling. Doppler echocardiography is a simple and effective mean to assess the hemodynamic effect of AV interval modulation in this setting.

Pacemakers

Rapid advances in pacing technology will continue to affect the quality of life of many patients with cardiovascular disease. A truly "smart" device that seemed fanciful 30 years ago now seems to be a virtual certainty by early in the next century. The surgical contributions and expertise of individuals trained in cardiothoracic surgery in these bradypacing developments is highly desirable to minimize morbidity to the greatest possible degree, to optimize the outcome of the procedure for the individual patient, and to conserve health care costs as much as possible. To maintain this cardiothoracic presence in cardiac pacing, acquisition of knowledge and expertise in the basic electrophysiology and technology of cardiac pacing, to go along with surgical expertise, is necessary on the part of individuals with the interest and opportunity to do so.

Echocardiographic Management of Patients With Hypertrophic Obstructive Ca rdiomyopathy Treated With Dual Chamber Pacemakers

A 53-year-old man diagnosed and treated for hypertrophic obstructive cardiomyopathy received serial echocardiograms before and after dual-chamber pacemaker implantation. Varying the programmed atrioventricular delay in a dual-chamber pacemaker can affect the left ventricular outflow tract pressure gradient in hypertrophic obstructive cardiomyopathy. Serial Doppler echo examinations were used to evaluate the effect of varying atrioventricular intervals. Echocardiography can be effectively used with pacemaker programming to optimize the left ventricular outflow tract velocities in patients with hypertrophic obstructive cardiomyopathy.