A high degree of heart rate (HR) variability is found in compensated hearts with good function, whereas HR variability can be decreased with severe coronary artery disease, congestive heart failure, aging and diabetic neuropathy. To test the hypothesis that HR variability is a predictor of long-term survival after acute myocardial infarction (AMI), the Holter tapes of 808 patients who survived AMI were analyzed. Heart rate variability was defined as the standard deviation of all normal RR intervals in a 24-hour continuous electrocardiogram recording made 11 +/- 3 days after AMI. In all patients demographic, clinical and laboratory variables were measured at baseline. Mean follow-up time was 31 months. Of all Holter variables measured, HR variability had the strongest univariate correlation with mortality. The relative risk of mortality was 5.3 times higher in the group with HR variability of less than 50 ms than the group with HR variability of more than 100 ms. HR variability remained a significant predictor of mortality after adjusting for clinical, demographic, other Holter features and ejection fraction. A hypothesis to explain this finding is that decreased HR variability correlates with increased sympathetic or decreased vagal tone, which may predispose to ventricular fibrillation.

Decreased heart rate variability and its association with increased mortality after acute myocardial infarction

To determine which preoperative factors might affect the development of cardiac complications after major noncardiac operations, we prospectively studied 1001 patients over 40 years of age. By multivariate discriminant analysis, we identified nine independent significant correlates of life-threatening and fatal cardiac complications: preoperative third heart sound or jugular venous distention; myocardial infarction in the preceding six months; more than five premature ventricular contractions per minute documented at any time before operation; rhythm other than sinus or presence of premature atrial contractions on preoperative electrocardiogram; age over 70 years; intraperitoneal, intrathoracic or aortic operation; emergency operation; important valvular aortic stenosis; and poor general medical condition. Patients could be separated into four classes of significantly different risk. Ten of the 19 postoperative cardiac fatalities occurred in the 18 patients at highest risk. If validated by prospective application, the multifactorial index may allow preoperative estimation of cardiac risk independent of direct surgical risk.

Multifactorial Index of Cardiac Risk in Noncardiac Surgical Procedures

Sleep-related breathing disorders are highly prevalent in patients with established cardiovascular disease. Obstructive sleep apnea (OSA) affects an estimated 15 million adult Americans and is present in a large proportion of patients with hypertension and in those with other cardiovascular disorders, including coronary artery disease, stroke, and atrial fibrillation.1–14 In contrast, central sleep apnea (CSA) occurs mainly in patients with heart failure.15–19 The purpose of this Scientific Statement is to describe the types and prevalence of sleep apnea and its relevance to individuals who either are at risk for or already have established cardiovascular disease. Special emphasis is given to recognizing the patient with cardiovascular disease who has coexisting sleep apnea, to understanding the mechanisms by which sleep apnea may contribute to the progression of the cardiovascular condition, and to identifying strategies for treatment. This document is not intended as a systematic review but rather seeks to highlight concepts and evidence important to understanding the interactions between sleep apnea and cardiovascular disease, with particular attention to more recent advances in patient-oriented research. Implicit in this first American Heart Association/American College of Cardiology Scientific Statement on Sleep Apnea and Cardiovascular Disease is the recognition that, although holding great promise, this general area is in need of a substantially expanded knowledge base. Specific questions include whether sleep apnea is important in initiating the development of cardiac and vascular disease, whether sleep apnea in patients with established cardiovascular disease accelerates disease progression, and whether treatment of sleep apnea results in clinical improvement, fewer cardiovascular events, and reduced mortality.

Experimental approaches directed at addressing these issues are limited by several considerations. First, the close association between obesity and OSA often obscures differentiation between the effects of obesity, the effects of OSA, and the effects of synergies between these conditions. Second, multiple comorbidities, …

Sleep Apnea and Cardiovascular Disease An American Heart Association/American College of Cardiology Foundation Scientific Statement From the American Heart Association Council for High Blood Pressure Research Professional Education Committee, Council on Clinical Cardiology, Stroke Council, and Council on Cardiovascular Nursing In Collaboration With the National Heart, Lung, and Blood Institute National Center on Sleep Disorders Research (National Institutes of Health)

THE development of a clinically applicable, automatic, implantable defibrillator has been described previously.1 This electronic device is designed to monitor cardiac electrical activity, to recogn...

Termination of Malignant Ventricular Arrhythmias with an Implanted Automatic Defibrillator in Human Beings

We examined the relationships among ventricular arrhythmias, left ventricular dysfunction, and mortality after the occurrence of myocardial infarction in 766 patients who enrolled in a nine-hospital study and underwent two special tests. Frequency and repetitiveness of ventricular premature depolarizations (VPDs) were determined by computer analysis of predischarge 24 hr electrocardiographic recordings. The left ventricular ejection fraction (LVEF) was determined by radionuclide ventriculography and dichotomized at its optimal value of 30%. Frequency of VPDs was divided into three categories: (1) less than one per hour, (2) one to 2.9 per hour, and (3) three or more per hour. Repetitiveness of VPDs was also divided into three categories: (1) no repetitive VPDs, (2) paired VPDs, and (3) VPD runs. These variables were related, one at a time and jointly, to total mortality and to deaths caused by arrhythmias. The hazard ratios for dying in the higher or highest risk stratum vs the lower or lowest stratum for each variable (adjusted for the effects of the others) were: LVEF below 30%, 3.5; VPD runs, 1.9; and VPD frequency of three or more per hour, 2.0. There were no significant interactions among the three variables with respect to effects on the risk of mortality. There was a suggestion of an interaction between each risk variable and time after infarction. LVEF below 30% was a better predictor of early mortality (less than 6 months) and the presence of ventricular arrhythmias was a better predictor of late mortality (after 6 months).(ABSTRACT TRUNCATED AT 250 WORDS)

The relationships among ventricular arrhythmias, left ventricular dysfunction, and mortality in the 2 years after myocardial infarction.

The role of ventricular dysrhythmias as determinants of sudden coronary death (SCD) was studied prospectively in 160 male survivors of myocardial infarction, all under 65 years of age and in New York Heart Association (NYHA) functional class I or II. Twelve-hour electrocardiographic recordings were taken in all patients at serial intervals and analyzed for frequency and type of ventricular ectopic beat (VEB). Eighty percent showed VEB's on at least one tape recording. There have been 14 SCD's in a follow-up period ranging between 30 and 54 months, 12 in 87 patients (13.8%) with significant VEB's (frequent, unifocal, multifocal, paired or coupled, and ventricular tachycardia), and only two in 66 patients (3%) with absent or infrequent VEB's (P < 0.02). Although the number of patients in this study is small, the results show that all complex VEB forms together were associated with an excess risk of SCD, notwithstanding the absence of SCD in 27 patients with ventricular parasystole. It is suggested that the ...

Prognostic Significance of Ventricular Ectopic Beats with Respect to Sudden Death in the Late Postinfarction Period

Disclosed are several embodiments of an electrode system for ventricular defibrillation, and the methods of using and implanting the electrode system. In one embodiment, the electrodes are in a generally base-apex configuration having a split conformal base electrode residing above the base of the ventricles (a transecting plane separating the atria from the ventricles) in the region of the atria and a conformal apex electrode in the form of a rotated conic section residing at the apex of the heart. In another embodiment, defibrillation is accomplished by the apex electrode acting against a catheter electrode situated high in the heart or in the superior vena cava. The electrodes themselves are in the form of planar metallic mesh elements adapted to lie in contact with body tissue on an active surface, insulated on the opposite surface. In another embodiment, the conductive portions of the respective electrodes are developed from metallic plates, exposed on one surface and insulated on the other. The electrodes may be split, or may entirely surround the base and apex of the heart. The disclosed electrode system is well adapted for easy implantation during an open heart surgery, or in a separate operation which can be performed in the mediastinal space without intrusion of the pleural space. The electrode system may be implanted for immediate stand-by defibrillation, or may be implanted during open heart surgery, used for post-operative monitoring, pacing and defibrillation, should the need arise, and then subcutaneously implanted for future association with an automatic defibrillating pulse generator. When employed after open heart surgery, the electrode system is preferably equipped with independent atrial and ventricular pacer electrodes. Also disclosed are techniques for fixing the electrode system to the surrounding body tissue, and electrode leads which may be removed after the implanted electrodes have served their desired function, without disturbing the electrodes themselves.

Implantable electrodes for accomplishing ventricular defibrillation and pacing and method of electrode implantation and utilization

A device for recording and subsequently reproducing information, such as desired portions of an ECG signal produced by a heart prior to and during the occurrence of a disturbance in cardiac electrical activity. Two basic embodiments of the inventive recorder are contemplated. One embodiment is fully implantable and is encased with sensing and defibrillating electronics. With this embodiment, a low-power, low-capacity, continually updated recorder is continually operative, and a high-capacity stand-by recorder is actuated upon the sensing of fibrillation. An external device is used to retrieve by telemetry, the information stored in the implanted recorder. The second embodiment of the inventive recorder is an external device which has external electrodes for associating with the patient; ECG information is transmitted to the recorder unit by telemetry. Here, because power consumption is not so critical as with the implantable embodiment, a delay-type continually updated memory is continuously operative. Then, when any one of several types of arrhythmias is sensed, or when a defibrillating pulse is delivered, the data in the memory is "permanently" recorded on magnetic tape. Either embodiment may be used with an implantable defibrillator to record and subsequently reproduce information relating to the operation of the implantable defibrillator. The second embodiment also has an alarm capability to warn the patient should there be an interruption in telemetric transmission.

Arrhythmia recorder for use with an implantable defibrillator

The effectiveness of low energy intraventricular catheter defibrillation was evaluated in 11 patients undergoing coronary artery surgery, in whom ventricular fibrillation occurred after anoxic arrest of 21-42 min. A distal electrode catheter was introduced through an atriotomy into the right ventricular apex. In eight patients the proximal electrode was a saline-soaked sponge placed on the superior vena cava, while in three this electrode formed an integral part of the superior vena cava cannula used in cardiopulmonary bypass. Intraventricular catheter defibrillation was accomplished in nine patients using 5-15 w-sec, considerably less energy than required for paddle defibrillation. There were no apparent short or long-term ill effects. Unsuccessful defibrillation in the two remaining patients was ascribed to difficulties in electrode placement. The effectiveness of low energy intraventricular catheter defibrillation in man, in addition to raising basic electrophysiologic questions, provides background fo...

Feasibility and Effectiveness of Low-Energy Catheter Defibrillation in Man

An externally controlled implantable electronic device for delivering a cardioverting pulse of energy to the atrium of an ailing heart. In one embodiment, the device is particularly suited for use when the patient visits the office of his physician, and contemplates the transmission of both information and powering energy through the skin of the patient. In another embodiment, the device can be readily operated at home, by the patient, and without the intervention of the physician. Here, the source of energy is permanently implanted.

Morton M. Mower

Papers

Prognostic Significance of Ventricular Ectopic Beats with Respect to Sudden Death in the Late Postinfarction Period

Implantable electrodes for accomplishing ventricular defibrillation and pacing and method of electrode implantation and utilization

Arrhythmia recorder for use with an implantable defibrillator

Feasibility and Effectiveness of Low-Energy Catheter Defibrillation in Man

Cardioverting device with stored energy selecting means and discharge initiating means, and related method