Predictors of stroke in patients paced for sick sinus syndrome

OBJECTIVES: This study was an analysis of factors associated with stroke in a population of patients paced for sinus node dysfunction in a large prospective clinical trial (Mode Selection Trial [MOST]). BACKGROUND: The effects of dual-chamber versus single-chamber ventricular pacing on subsequent stroke in patients with sinus node dysfunction are not known. METHODS: A total of 2,010 patients with sinus node dysfunction were randomized to ventricular or dual-chamber pacing and followed for a median of 33.1 months. RESULTS: The median participant age was 74 years. During 5,664 patient-years of follow-up, 90 strokes (11 hemorrhagic) occurred. By life-table analysis, the rate of stroke was 2.2% (95% confidence interval [CI] 1.6 to 2.9) at one year and 5.8% (95% CI 4.5 to 7.1) at four years. The incidence of stroke was not significantly different in dual-chamber (4%) as compared with ventricular-paced patients (4.9%) (hazard ratio [HR] 0.82, 95% CI 0.54 to 1.25, p = 0.36). Multivariable analysis demonstrated that significant predictors of stroke included prior stroke or transient ischemic attack, Caucasian race, hypertension, prior systemic embolism, and New York Heart Association functional class III or IV (p < 0.05); pacing mode remained non-significant after adjustment for these factors (p = 0.37). Clinically reported atrial fibrillation after implantation was a risk factor for stroke in this cohort after adjustment for other predictors of stroke (p = 0.042, HR 1.68 [95% CI 1.02 to 2.76]). CONCLUSIONS: Clinical characteristics, but not mode of pacing, were associated with subsequent stroke in patients paced for sinus node dysfunction.     

Prognosis of patients permanently paced for sick sinus syndrome.

In 39 patients (mean age, 66 years) treated for sick sinus syndrome (SSS) with pacemaker insertion, the long-term prognosis was studied. Fifteen patients (42%) died during the follow-up period of 6 to 59 months (mean, 25 months). Three patients were unavailable for follow-up. Eleven of the 15 deaths (73%) were cardiac-related, yet none could be associated with either an arrhythmia or pacemaker failure. Symptoms recurred or persisted after pacemaker insertion in 14 patients (mean age, 71 years), nine of whom died (31 deaths per 100 patient follow-up years). Twenty-two patients (mean age, 63 years) were asymptomatic after pacer insertion, six of whom died (11 deaths per 100 patient follow-up years). These follow-up results demonstrate a poor long-term prognosis in patients with SSS and persistent symptoms following permanent pacing.     

Carotid sinus syndrome and falls in older adults

Retrospective and circumstantial evidence supports an overlap between symptoms of falls and syncope in older adults. Because of this overlap, we undertook a prospective, explanatory, single-center study of cardiac pacing for falls in patients with carotid sinus syndrome in a consecutive series of over 56,000 adult visitors to an emergency department. One third attended because of a fall; one in five fallers had unexplained falls, and one third of these had carotid sinus hypersensitivity, of whom one half had a cardioinhibitory or mixed response that may be expected to respond to cardiac pacing. In a randomized, controlled trial of a subset of these patients, cardiac pacing was shown to significantly reduce subsequent fall rates by two thirds and syncopal rates during 1-year follow-up. The current pacing rate for carotid sinus syndrome is much higher in our practice than in other series because our facility is dedicated to falls and syncope in older subjects who have direct access to referring physicians and family practitioners. Of the implants in our region, 24% are for carotid sinus syndrome, compared with 43% for atrioventricular block, 20% for sick sinus syndrome, and 12% for atrial fibrillation. These rates do not include pacing in patients who fall, but rather reflect pacing rates consistent with American College of Cardiology guidelines for carotid sinus syndrome, such as recurrent syncope. These preliminary results from a local explanatory study are now being tested in a multicenter study entitled Syncope and Falls in the Elderly: Pacing and Carotid Sinus Evaluation (SAFE-PACE II).     

Cerebral hemodynamics in carotid sinus syndrome and atrioventricular block

Carotid sinus syndrome (CSS) is a cause of syncope due to exaggerated baroreceptor-mediated cardioinhibitory/vasodepressive reflexes. We sought to determine if cerebral hemodynamics and regulation were specifically altered in these patients by comparison with pure asystole without vasodepression in patients with atrioventricular block (AVB). Mean blood flow velocity (transcranial Doppler sonography) and mean arterial blood pressure (Finapres) were recorded during cardioinhibition induced by carotid massage in patients with CSS (n = 14, 75 +/- SD 8 years) and asystole induced by temporary pacemaker inhibition in patients with complete AVB (n = 10, 69 +/- 11 years). Cerebrovascular resistance was estimated by the arterial pressure/cerebral flow velocity ratio, and dynamic cerebral autoregulatory responses were determined by the rate of regulation and autoregulatory index. Asystole and cardioinhibition each induced a decrease in arterial pressure (CSS 55 +/- 9% vs AVB 40 +/- 14%, p <0.05) and cerebral flow velocity (CSS 66 +/- 19% vs AVB 69 +/- 14%, p = NS), with an initial transient increase in cerebrovascular resistance (CSS 102 +/- 136% vs AVB 128 +/- 92%, p = NS) followed by a decrease (CSS 38 +/- 12%, AVB 29 +/- 13%, p = NS). The rate of regulation and autoregulatory index were higher with AVB (0.43 +/- 0.20 and 8.5 +/- 1.1 second(-1)) than CSS (0.20 +/- 0.12 and 4.8 +/- 1.3 second(-1), respectively, p <0.01 and p <0.001 vs AVB). During asystole and vasodepression, cerebral hypoperfusion in CSS is normally compensated for by cerebral autoregulation. The lower rate of regulation in CSS compared with AVB likely results from persistent peripheral vasodepression triggered by carotid massage.     

病态窦房结综合征患者房室传导功能分析

为了解病态窦房结综合征患者的房室传导功能,用食管电生理检查观察窦房结功能正常者86例、窦房结功能低下者40例和病态窦房结综合征者109例的房室传导功能.结果显示:3组的文氏型阻滞点、2:1阻滞点差异无显著意义(P>0.05).将窦房结功能障碍者的窦房结恢复时间与文氏型阻滞点、2:1阻滞点作相关分析,结果均无相关性(P>0.05).认为病态窦房结综合征发生房室传导阻滞的概率较低,植入起搏器前应作食管心房调搏检查房室传导系统功能.     

The importance of the autonomic nervous system for sinus and atrioventricular node function in patients with sick sinus syndrome

Autonomous nervous system (ANS) influence on sinus (SN) and atrioventricular (A-V N) nodes is still under investigation, especially in pathological states. We analysed role of ANS for SN and A-VN function in patients with different forms of sick sinus syndrome (SSS). From 310 patients (pts) after electrophysiological examinations before and after pharmacological denervation of the heart we selected 206 pts with SSS (group S) for further investigation. In group S were 124 men and 82 women from 17 years old (mean 46 +/- 16). Coronary heart disease was present in 102 pts (myocardial infarction in 7), mitral valve prolapse in 10, hypertrophic cardiomyopathy in 2. SSS was the only pathological finding in 75 pts. In 92 cases pacemaker was implanted (45%) of whole group S. Only sinus bradycardia was observed in 118 cases, tachycardia-bradycardia syndrome in 34 and sinus arrest or/and sinoatrial block in 53 cases. Electrophysiological examinations were performed using transesophageal stimulation of the left atrium before and after denervation of the heart. Pharmacological denervation of the heart was obtained by propranolol (i.v. 0.2 mg/kg body weight) and than atropine (i.v. 0.04 mg/kg body weight). We analysed sinus cycle length in basic state, after propranolol injection and after full denervation, maximal sinus nodes recovery time, maximal corrected sinus node recovery time, secondary pause, sino-atrial conduction time, Wenckebach point before and after full denervation. The whole group with SSS (group S) was divided: pts with normal (S1) and abnormal (S2) intrinsic properties of SN (104 and 102 pts respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognosis of patients paced for chronic atrioventricular block.

Between the years 1960 and 1974, 839 patients were paced for chronic complete atrioventricular block. Analysis of survival compared with the general population showed that 170 deaths were expected according to standard mortality tables and 288 actually occurred, giving a ratio of actual to expected deaths of 1.7:1. Patients with a definite history of myocardial infarction showed a higher than average mortality when paced. Mortality was not influenced whether heart was constant or intermittent, whether the ventricular rate was below or above 40/minutes, or whether QRS duration was greater or less than 0.1 second. Analysis of the age groups paced disclosed the most important correlations. Between the ages of 80 and 89 years paced patients could expect to survive as long as other of the same age without heart block. There was, however, a very high ratio of 4.5:1 for 90 patients in the age group 50 to 59 years. The reason for the high mortality ratio was uncertain but it may have been the result of a greater incidence of underlying coronary artery disease.     

Prognosis of patients paced for chronic atrioventricular block.

Between the years 1960 and 1974, 839 patients were paced for chronic complete atrioventricular block. Analysis of survival compared with the general population showed that 170 deaths were expected according to standard mortality tables and 288 actually occurred, giving a ratio of actual to expected deaths of 1.7:1. Patients with a definite history of myocardial infarction showed a higher than average mortality when paced. Mortality was not influenced whether heart was constant or intermittent, whether the ventricular rate was below or above 40/minutes, or whether QRS duration was greater or less than 0.1 second. Analysis of the age groups paced disclosed the most important correlations. Between the ages of 80 and 89 years paced patients could expect to survive as long as other of the same age without heart block. There was, however, a very high ratio of 4.5:1 for 90 patients in the age group 50 to 59 years. The reason for the high mortality ratio was uncertain but it may have been the result of a greater incidence of underlying coronary artery disease.     

Carotid sinus hypersensitivity in asymptomatic older persons: implications for diagnosis of syncope and falls

BACKGROUND: Carotid sinus hypersensitivity is the most commonly reported cause of falls and syncope in older persons. Recent guidelines recommend 5 to 10 seconds of carotid sinus massage in supine and upright positions with beat-to-beat monitoring. The aim of this study was to determine the prevalence of carotid sinus hypersensitivity in (1) an unselected community sample of older people and (2) a subsample with no history of syncope, dizziness, or falls using recently standardized diagnostic criteria. METHODS: One thousand individuals older than 65 years were randomly sampled from a single general practice register; 272 participants underwent supine and upright carotid sinus massage with continuous heart rate and phasic blood pressure monitoring. Carotid sinus hypersensitivity was defined as asystole of 3 seconds or greater and/or a drop in systolic blood pressure of 50 mm Hg or greater. RESULTS: Carotid sinus hypersensitivity was present in 107 individuals (39%); 24% had asystole of 3 seconds or greater during carotid sinus massage; and 16% had symptoms (including syncope) with carotid sinus hypersensitivity. Age (odds ratio, 1.05; 95% confidence interval, 1.00-1.09) and male sex (odds ratio, 1.71; 95% confidence intervals, 1.04-2.82) were the only predictors of carotid sinus hypersensitivity. In 80 previously asymptomatic individuals, carotid sinus hypersensitivity was present in 28 (35%) and accompanied by symptoms in 10. The 95th percentile for carotid sinus massage response was 7.3 seconds' asystole and a 77-mm Hg drop in systolic blood pressure. CONCLUSIONS: Carotid sinus hypersensitivity is common in older persons, even those with no history of syncope, dizziness, or falls. The finding of a hypersensitive response should not necessarily preclude further investigation for other causes of syncope.     

Arrhythmogenic right ventricular dysplasia with sick sinus syndrome and atrioventricular conduction disturbance

Although arrhythmogenic right ventricular dysplasia (ARVD) is believed to involve primarily the right ventricle, left ventricular abnormalities have also been described. We report a case of ARVD with abnormalities of the sinus node, right atrium and atrioventricular node. The biopsies taken from the right atrium and the right ventricle showed replacement of myocardium by fibrous tissue. The pathologic changes of this disease process may extend into the atrium and atrioventricular node.