Charles Fisch

Relation of Electrolyte Disturbances to Cardiac Arrhythmias

While a number of electrolytes play a role in the genesis of the transmembrane action potential (AP), the changes in the action potential most clearly related to arrhythmias are dependent to a large extent on K+. Potassium gradient is a major determinant of the magnitude of transmembrane resting potential (TRP), and secondarily the rate of rise (dV/dt) of phase 0, and consequently the speed of conduction. The cell membrane conductance for K+, or a decrease therein, is most likely the major determinant of spontaneous slow depolarization during phase 4. Thus K+ has a pronounced effect on both conduction and automaticity. Furthermore, these electrophysiologic properties are altered within levels of K+ encountered in clinical medicine, a situation which, with rare exceptions, is not seen with Ca++, Mg++, or Na–. These latter ions affect the action potential and induce experimental arrhythmias at concentrations which are unphysiologic and frequently incompatible with life. Consequently, of all the electrolytes...

Cardiac arrhythmias observed during maximal treadmill exercise testing in clinically normal men

Abstract The incidence of cardiac arrhythmias observed during maximal treadmill exercise testing was studied in 650 men aged 25 to 54 years. In 561 there was no clinical evidence of cardiovascular disease; 89 were classified as having definite or suspected cardiovascular disease. The patients were divided into 3 age groups—25 to 34, 35 to 44 and 45 to 54 years—to define any age-related differences in the incidence of arrhythmias during exercise. Single or consecutive ventricular premature complexes were observed in 31 percent of the 25 to 34 year olds, 38 percent of the 35 to 44 year olds and 49 percent of the 45 to 54 year olds; the incidence of supraventricular premature complexes was 7, 10 and 14 percent, respectively. The incidence of both ventricular and supraventricular complexes increased with age. For any given age group the incidence of ventricular premature complexes was greater in patients with definite or suspected cardiovascular disease. These patients were more prone to demonstrate frequent ventricular premature complexes and had a higher incidence of multifocal ventricular premature beats and ventricular tachycardia. The ventricular premature complexes were also more likely to appear at lower heart rates during exercise in patients with cardiovascular disease. However, the appearance of unifocal ventricular premature complexes during maximal or near maximal exercise testing should not be equated with the presence of clinically significant cardiac disease.

Repetitive Ventricular Arrhythmia Resulting from Artificial Internal Pacemaker

We have presented a case summary of a patient in whom several periods of repetitive ventricular arrhythmia—at times indistinguishable from fibrillation—were induced by artificial internal pacemaker stimuli falling in the T wave of a preceding cycle (the vulnerable period). Ours is the third such case to be reported and, although this repetitive response is said to be rare, the exact incidence remains to be determined. The theoretical and clinical implications are discussed and possible explanations are given for why such small artificial stimuli are capable of evoking such serious arrhythmias in certain patients. We also have suggested measures that might reduce the likelihood for this complication to arise.

Atrial myxoma: II. Phonocardiographic, echocardiographic, hemodynamic, and angiographic features in nine cases

Abstract Nine cases of atrial myxoma, seven left and two right, have been diagnosed and successfully treated in the past five years. The phonocardiographic, echocardiographic, hemodynamic, and angiographic features are discussed in detail.

Guidelines for implantation of cardiac pacemakers and antiarrhythmia devices. A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures. (Committee on Pacemaker Implantation).

It is becoming more apparent each day that despite a strong national commitment to excellence in health care, the resources and personnel are finite. It is therefore appropriate that the medical profession examine the impact of developing technol9gy on the practice and cost of medical care. Such. analysis, carefully conducted, could potentially have an impact on the cost of medical care without diminishing the effectiveness of that care. To this end, the American College of Cardiology and the American Heart Association in 1980 established a Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures with the following charge: The Task Force of the American College of Cardiology and the American Heart Association shall define the role of specific noninvasive and invasive procedures in the diagnosis and management Qf cardiovascular disease. The Task Force shall address, when appropriate, the contribution, uniqueness, sensitivity, specificity, indications, contraindications and cost-effectiveness of such specific procedures. The Task Force shall include a Chairman and six members, three representatives from the American Heart Association, and three representatives from

Observations on the cardiovascular involvement in Friedreich's ataxia

Abstract The case of a young man with Friedrichs ataxia who died of intractable atrial arrhythmias and cardiac failure is presented. At necropsy there was widespread involvement of the small arteries of the myocardium (including the cardiac conduction system) and lungs. After critical review of previous necropsy studies in this disease, it is suggested that the most likely explanation for the cardiopathy of Friedreichs ataxia is obliteration of the small coronary arteries. Potential significance of the pulmonary arteriopathy is briefly discussed.

Atrial myxoma. I. Clinical and pathologic features in nine cases.

Abstract During the past five years, nine cases of atrial myxoma, seven left and two right, have been diagnosed and successfully treated at this institution. Seven were female and all were Caucasian except for one Negro man. Dyspnea was the most common symptom, being present in all nine patients. Six of the nine complained of vague chest pain and syncope was present in three. Ankle edema was prominent in eight patients. Emboli, pulmonary and/or systemic, occurred in four patients. Congestive heart failure, right and/or left, was present in eight of the nine; no patient complained of hemoptysis. Four patients were found to have anemia and three noted fever. The atrial myxoma was successfully removed with the aid of cardiopulmonary bypass and all nine patients noted marked symptomatic improvement. The clinical, electrocardiographic, and pathologic features are described.

Effects of Acetylcholine on Automaticity and Conduction in the Proximal Portion of the His-Purkinje Specialized Conduction System of the Dog

Conventional intracellular recordings from the bundle of His and right bundle branch of the canine heart demonstrated that the slope of diastolic depolarization is markedly depressed by superfusion with relatively small concentrations (4−8 μg/ml) of acetylcholine. As the cells become less automatic, take-off potential increases, rise time of phase 0 is reduced, action potential amplitude increases, and conduction proceeds more rapidly.

Heart rate variability for risk stratification of life-threatening arrhythmias

[The following is a position statement prepared by the Cardiovascular Technology Assessment Committee: LEONARD S. DREIFUS, MD, FACC, Chairman, JAI B. AGARWAL, MBBS, FACC, ELIAS H. BOTVINICK, MD, FACC, KEITH C. FERDINAND, MD, FACC, CHARLES FISCH, MD, FACC, ex officio, JOHN D. FISHER, MD, FACC, J. WARD KENNEDY, MD, FACC, ex officio, RICHARD E. KERBER, MD, FACC, CHARLES R. LAMBERT, MD, FACC, OKIKE N. OKIKE, MD, FACC, ERIC N. PRYSTOWSKY, MD, FACC, SANJEEV V. SAKSENA, MBBS, FACC, JOHN S. SCHROEDER, MD, FACC, ex officio, DAVID O. WILLIAMS, MD, FACC. This position statement was approved by the Board of Trustees of the American College of Cardiology on March 13, 1993. Reprints are available from: Educational Products Sales and Marketing; 9111 Old Georgetown Road; Bethesda, MD 20814; 800/257-4740.]

Congenital absence of the left pericardium. Clinical, electrocardiographic, radiographic, hemodynamic, and angiographic findings in six cases.

Until the past decade, the diagnosis of congenital absence of the pericardium, partial or complete, had rarely been made prior to postmortem examination or thoracotomy. Since 1963, the condition has been recognized during life in six patients at this institution. Of these six patients, two had partial absence of the left pericardium and four had complete absence of the left pericardium. Characteristic roentgenologic findings were present in all six patients. Associated heart lesions were not present in either patient with a partial pericardial defect. Two of the remaining four had associated heart lesions. One patient had surgical repair of an atrial septal defect. Surgical repair of the pericardial defect was not attempted in any of the six patients. Hemodynamic determinations at rest were normal in all six patients. The two patients with partial pericardial defects, however, had elevation of the pulmonary artery and left ventricular end-diastolic pressures during mild exercise in the recumbent position which suggests that this type of defect is not totally innocuous. In view of the unusual and extreme cardiac mobility in this condition, it is conceivable that a portion of the heart could herniate and transiently incarcerate through the partial defect during exercise. It is suggested that partial pericardial defects may warrant surgical repair. Small defects or complete absence of the left pericardium, however, are apparently without lethal potential and do not require surgical intervention.