Characteristics of sinoatrial conduction in patients with coronary artery disease

Coexistent coronary artery disease in Indian patients undergoing permanent pacemaker implantation (PPI) for symptomatic bradyarrhythmia

Background

The cause-effect of conduction disturbance in chronic lesion of coronary arteries is complicated. This study was designed to evaluate coexistent CAD in patients with symptomatic bradyarrhythmia to find common anatomic basis for conduction disturbances and its relationship to conventional coronary risk factors.

Methods

In this prospective observational study, 929 patients who admitted for symptomatic bradyarrhythmia requiring permanent pacemaker implantation were included. All included patients underwent coronary angiography and were divided into groups based on angiographic findings. Association between conduction disturbances and these groups were analyzed.

Results

A total of 929 patients with mean age of 63.1 years were included in our study. We found age ≥50 years, male sex, presence of diabetes and hypertension as statistically significant predictors of abnormal coronary angiography. Obstructive CAD (≥50% stenosis) was found in 34.4% patients. Prevalence of single vessel disease, double vessel disease and triple vessel disease was 15.3%, 10.2% and 8.9% respectively. Severe coronary obstruction (≥90% obstruction) was found in 16.25% patients. Revascularization was advised in three fourth of cases of obstructive CAD. Approximately two third of patients didn’t have significant obstruction in coronaries supplying the conduction system. Type 4 was the commonest anatomy in obstructive CAD. SA Nodal artery was found more diseased in patients of SSS with p value of 0.01.

Conclusion

Obstructive CAD was found in one third of patients undergoing PPI. Age ≥50 years, male sex, diabetes and hypertension were found significantly correlated with presence of CAD and may act as important markers for the judgment of further coronary evaluation.

Sinus dysfunction after stent implantation in the right coronary artery immediately recovered after reflow in the sinus node artery

A 67-year-old man who had a history of syncope was admitted because of effort angina. The sinus node (SN) was the single blood supply from the right coronary artery (RCA). After we implanted 2 everolimus-eluting stents for RCA, slow-flow occurred and the SN artery was occluded, and junctional escape rhythm was sustained. After the wiring to the occluded SN artery, junctional escape rhythm immediately recovered to sinus rhythm, and the patient achieved continuous sinus rhythm and stable hemodynamics. Given that acute SN ischemia is a possible cause of sinus dysfunction, careful choice of a percutaneous coronary intervention strategy should be taken into consideration if the SN artery is the single blood supply from the RCA and if syncopal history is present.

Atrial Coronary Arteries: Anatomy And Atrial Perfusion Territories

Coronary anatomy has traditionally focused on ventricular circulation. This is largely due to the extent to which coronary artery disease contributes to ischemic heart disease through ventricular myocardial damage. Atrial fibrillation and other tachyarrhythmias that involve the atria, however, remain a major cause of morbidity and mortality. In order to increase mechanistic research and therapeutic interventional procedures for diseases of the atria, an optimal knowledge of atrial anatomy is necessary. While substantial clarity exists regarding the distribution of nerve terminals and the organization of muscle bundles, the anatomy of coronary atrial circulation remains understudied. Historically, the high anatomical variability of atrial coronary branches led to unstandardized nomenclature in the literature. In this review, we delineate the anatomic courses of key atrial coronary branches and their perfusion territories, clarify their nomenclature, and propose unifying anatomical concepts of atrial circulation that we believe to be critical to the success of modern electrophysiologic and surgical procedures.

Sudden death under successful medical management of sick sinus syndrome after cardiac pacing discontinuation

Bacterial infection is a serious complication of permanent pacemaker implantation. A 52-year-old woman with sick sinus syndrome and vasospastic angina developed pacemaker infection 4 years after implantation, with methicillin-resistant Staphylococcus aureus detected in arterial blood cultures. We treated the septicemia with antibiotics and removed the infected pacemaker. We treated sick sinus syndrome with intravenous nitroglycerin followed by oral maintenance isosorbide mononitrate. After cardiac pacing was discontinued following removal of the infected permanent pacemaker, the patient remained well, until her sudden death 3.5 years later. Although the precise cause of death was not clear, we suspected sick sinus syndrome or vasospastic angina, and now consider the outcome may have been more favorable if we had reimplanted a permanent pacemaker before she died.

The incidence of coronary artery disease in patients with symptomatic bradyarrhythmias

Symptomatic bradyarrhythmia occurs most often in aged patients. Most of these patients have multiple coronary risk factors and present with angina-like symptoms. The coexistence of CAD not only has major effects on their prognosis but also influences the long-term care. This study was designed to evaluate the incidence of coexistent CAD in patients with symptomatic bradyarrhythmias and its relationship to conventional coronary risk factors in Chinese people. From May 1996 to April 1998, we prospectively studied all consecutive patients admitted to our institution for symptomatic bradyarrhythmias requiring permanent pacemaker implantation. Coronary angiographies were performed non-selectively at the same session of pacemaker implantation. Based on the presence or absence of CAD, patients were divided into two groups for analysis. Multivariate logistic regression analysis was performed to determine independent predictors of CAD including sex, age, diabetes mellitus (DM), hypertension, hypercholesterolemia, and smoking. The odds-ratio (OR) and 95% confidence interval (CI) were determined. A total of 113 patients [68 males and 45 females, mean age 70.4+/-8.2 years old (range 45-86)] were included in our study. The diagnosis was sick sinus syndrome in 69 patients (61%) and atrioventricular block in 44 patients (39%). The incidence of CAD based on coronary angiography was 20%. The nodal-related artery was seldom involved among patients with coexistent CAD and symptomatic bradyarrhythmias (9%), and most patients had significant stenosis over LAD (74%). The baseline characteristics and presenting symptoms were not different statistically between patients with or without CAD. Hypercholesterolemia (OR 6.6, 95% CI 2.0-22.2, p=0.002) and DM (OR 4.7, 95% CI 1.3-17.2, p=0.020) were the two most significant independent predictors of CAD. In our patients with symptomatic bradyarrhythmias requiring permanent cardiac pacing, the incidence of CAD was 20% as determined by coronary angiography (CAG). Hypercholesterolemia and DM were the two most significant independent predictors for CAD in these patients. The nodal artery was seldom involved in patients with coexistent CAD and symptomatic bradyarrhythmias.

Disorders of Sinus Function

Sinus node dysfunction is a common entity with significant clinical implications. Establishing a diagnosis may, on occasion, tax the skills of the clinician. Many causes have been cited, but no single factor appears to be established. Immunologic abnormalities may play a part in the etiologic process. Clinical invasive electrophysiology studies may be used to establish a diagnosis. In general, medical therapy must be integrated. Controversy exists regarding the best method of permanent pacing. Treatment may need to be individualized to the type of arrhythmia noted. Long-term prognosis is a large factor in choice of therapy, related to the underlying disease. Prevention of atrial fibrillation may occur with dual-chamber pacing; however, anticoagulation appears essential in this patient subgroup. The 5-year mortality rate in these patients is high and does not appear to be significantly improved with artificial pacing. Mortality is prominently influenced by the coexistence of cardiovascular and valvular heart disease. Patients who die do not differ substantially from survivors with regard to type of sinus dysfunction, occurrence of tachyarrhythmia, or distal conduction abnormalities. The survival rate in patients with sick sinus syndrome and congestive heart failure is significantly lower, and the incidence of embolic events remains high in patients with permanent pacing and the sick sinus syndrome. Thus, it has been proposed that all patients exhibiting the bradycardia-tachycardia syndrome be fully anticoagulated. The incidence of atrial fibrillation is significantly lower in patients with atrial demand pacing (22.3% versus 3.9%) than in patients with ventricular pacing and is accompanied by a decreased incidence of systemic embolization (13% versus 1.6%). Reports comparing survival with use of dual-chamber pacing versus ventricular pacing are encouraging in patients with congestive heart failure. At present, the natural history of the disease is unknown; furthermore, clinical risk factors for the development of symptoms have not been defined, and no electrophysiologic measure of sinus node function has been demonstrated to have reliable predictive value. Therefore, common practice has been to withhold pacemaker therapy in the asymptomatic patient.

Bradycardia after heart transplantation: reversal with theophylline

OBJECTIVES

We attempted to demonstrate that theophylline, an adenosine receptor antagonist, can reverse bradyarrhythmias after orthotopic heart transplantation.

BACKGROUND

Sinus node dysfunction, primarily sinus bradycardia, frequently occurs after orthotopic heart transplantation and may lead to permanent pacemaker implantation. Endogenous adenosine has been implicated as a cause of such posttransplantation bradyarrhythmia.

METHODS

Twenty-nine transplant recipients (group 1) were given theophylline after bradyarrhythmias developed after transplantation. Data in these patients were compared with those in a control group of 18 patients without bradyarrhythmias (group 2) who were not given theophylline.

RESULTS

The mean heart rate in group 1 increased from 62 +/- 7 to 89 +/- 10 beats/min after administration of theophylline (p < 0.0001); the mean heart rate in group 2 was 88 +/- 12 beats/min. Patients in group 1 required more days of temporary atrial pacing (3.5 +/- 1 vs. 1.5 +/- 3, p < 0.04) before the administration of theophylline than did patients in group 2. The length of hospital stay after transplantation did not differ significantly between groups 1 and 2 (17 +/- 7.5 vs. 20 +/- 16 days, p = NS). Age, gender, underlying disease, preoperative use of amiodarone, graft ischemia time or the incidence of moderate to severe rejection were not different between patient groups.

CONCLUSIONS

The use of theophylline for posttransplantation bradyarrhythmias increased heart rate and facilitated the withdrawal of chronotropic support. We conclude that theophylline offers effective and specific therapy for heart transplant patients with early bradyarrhythmias, reducing the need for implantation of a permanent pacemaker.

Role of sinus node artery disease in sick sinus syndrome in inferior wall acute myocardial infarction

This study was undertaken to evaluate a possible role of sinus node (SN) artery disease in the pathogenesis of sick sinus syndrome (SSS) in patients with an inferior wall acute myocardial infarction (AMI). Coronary angiography and electrophysiologic studies of the SN, both in the basal state and after pharmacologic autonomic blockade, were performed in 23 study patients (mean age 60 years) with SSS and a previous inferior wall AMI and in another 23 control patients (mean age 57 years) with normal sinus rate and a previous inferior AMI. Stenosis of the SN artery (or that proximal to its origin) greater than 50% was present in 13 study patients (56%) and in 8 control patients (34%) (p less than 0.05). In the study group, the intrinsic heart rate was abnormal in 5 of the 6 patients (83%) with severe SN artery stenosis (greater than or equal to 75% narrowing), in 3 of the 7 (43%) with moderate stenosis (50 to 75% narrowing) and in 3 of the 10 (30%) with insignificant stenosis (less than 50% narrowing). In the study group, the correlation between the SN measures (heart rate, corrected SN recovery time and sinoatrial conduction time) and the severity of SN artery stenosis was good after autonomic blockade (r between 0.59 and 0.64) and poor in the basal state. These data provide evidence for a role of SN artery disease in the pathogenesis of SSS in patients with an inferior wall AMI.

Exercise testing in the diagnosis of sick sinus syndrome in the elderly: implications for treatment

Twenty-three elderly patients underwent treadmill exercise testing to fatigue; 11 patients had sick sinus syndrome (7 males, 4 females; age range 71-91 years; mean, 78 years); 12 elderly persons were controls (5 males, 7 females; age range 70-93 years; mean, 76 years). All were euthyroid. The study showed that patients with sick sinus syndrome compared with the control group demonstrated a lower resting heart rate, a smaller increase in heart rate during exercise, poorer exercise tolerance, and differences in heart rate during the recovery phase. The value of the effort test in relation to the diagnosis of sick sinus syndrome is discussed, together with its possible implications in the choice of pacemaker.

Sick sinus syndrome: an adenosine-mediated disease

It is suggested that adenosine is a mediator of the paroxysmal bradycardias and tachycardias characterising the sick sinus syndrome. Increased sensitivity to adenosine could account for the arrhythmias, which might therefore be suppressed by an adenosine antagonist such as theophylline.

A second zone of compensation during atrial premature stimulation: evidence for decremental conduction in the sinoatrial junction

125 consecutive patients with premature atrial stimulation were studied. Three demonstrated sinus node return cycles that were fully compensatory following premature atrial stimuli delivered early in diastole. This second zone of compensation was unaccompanied by significant alterations in the post-return cycle lengths or in P-wave morphology of the return cycle. To account for the occurrence of a complete compensatory pause following very early premature atrial depolarizations, we consider the possibility that retrograde conduction of the early atrial premature depolarization (APD) in the sinoatrial junction was delayed for a sufficient length of time to allow the sinus node to depolarize spontaneously on schedule. Collision between the APD and sinus beat would then occur despite the marked prematurity of the APD. Thus, the early APD had encountered the relative refractory period of the sinoatrial junction, suggesting that decremental conduction takes place within the sinoatrial region in man. These findings imply that there is the potential for reentry in the region of the human sinoatrial junction.

Pacemakers, cardiac mapping and EEG in the community hospital: a concise review of background and basic technical considerations

The heart is a pump. The objective of cardiac pacing is to improve the cardiac output. The most popular method of cardiac pacing (RV) is not physiologic and results in reduced stroke output when compared to that of normal sinus or atrial paced rhythm. Recognition of pacemaker induced low output states and pacemaker aggravated neurological symptoms has quickened interest in physiologic atrial pacing. The increased complexity of atrial pacing has been discouraging in the past, but technical advances in electrode and pacemaker design are promising. Selection of the optimal pacing site appears critical and requires the determination of the focal electrical potential and stimulating threshold before electrodes are positioned. With minimal expense, the EEG can be adapted for this type of cardiac mapping in the community hospital.

Acute ischemic sinus node dysfunctions in dogs

The effects of the occlusion of the two main atrial arteries irrigating the sinus node on sinus rhythm and postpacing sinus recovery were studied in 12 anesthetized dogs. Records of spontaneous rhythm and of postpacing sinus recovery were taken at control and hourly for 6 hours after the occlusion. The spontaneous cycle length (AA interval) was 335 +/- 11 ms at control and 416 +/- 17 ms (mean +/- SE) (p less than 0.005) one hour after the occlusion. It remained nearly unchanged during the following 5 hours of observation. The occlusion also shortened atrioventricular conduction time (AV interval) and reduced P-wave amplitude in ECG lead II in 9 of these dogs. While the control postpacing sinus recovery time was 397 +/- 13 ms, the 1-hour value was 715 +/- 165 ms. This prolongation persisted during the first four postocclusion hours but was less marked during the last two hours of observation. Moreover, the postpacing mode of return of the AA intervals to their prepacing value (sinus recovery pattern) became characteristically slow and progressive after occlusion, complete postpacing recovery often occurring only after 100 or more beats. Sequences of escape atrial and/or AV junctional rhythms were frequently seen during this recovery. Atrial extrasystoles and short sequences of atrial tachycardias were observed in most dogs after occlusion. Conversely, none of these changes occurred during a 6-hour experimental time in 5 control dogs in which the same protocol, occlusion excepted, was repeated. These observations show that the sinus node function in the dog is consistently affected by impairing its blood supply. Ischemic dysfunctions include sinus slowing, pacemaker shift, prolonged sinus recovery time, delayed postpacing recovery and supraventricular tachyarrhythmias.

Sinus bradycardia in the aged

In the aged, sinus bradycardia represents the sinus-node-dysfunction component of diffuse conduction system disease associated with coronary and cerebral arteriosclerosis. Findings are presented on 15 patients whose ages ranged from 69 to 93 years at the time of admission to a home for the aged. They remained under observation (with electrocardiographic data) for from less than 1 year up to 18 years. The findings illustrate the evolution of conduction system abnormalities, including sinus node dysfunction, occurring either as an initial or an interval event. These abnormalities represent positive indications for pacemaker insertion in the aged.