Te-Chuan Chou

Electrocardiographic Diagnosis of Right Ventricular Infarction

The electrocardiographic findings in 11 cases of acute right ventricular infarction associated with acute left ventricular inferior wall myocardial infarction are described. The diagnosis of right ventricular infarction was proved by autopsy findings in five cases and supported by hemodynamic data in the other six. Ten of the 11 patients had typical electrocardiographic changes of acute inferior myocardial infarction and one had that of inferior wall injury. Transient S-T segment elevation was present in one (lead V1) or more of the right precordial leads in eight cases. In the absence of other explanations for the S-T segment elevation, acute right ventricular infarction was most likely the cause. Therefore, when acute inferior myocardial infarction is accompanied by S-T segment elevation in the right precordial leads, the coexistence of right ventricular infarction should be suspected. The sensitivity and specificity of this electrocardiographic sign are yet to be determined.

Unreliability of conventional electrocardiography monitoring for arrhythmia detection in coronary care units

To evaluate the reliability of conventional coronary care unit electrocardiographic monitoring, a study was made of 31 consecutive patients with uncomplicated verified acute myocardial infarction. All patients were monitored routinely with conventional equipment, and at the same time the electrocardiogram for each patient was recorded continuously on electromagnetic tape and stored for later analysis by an automated arrhythmia detection system. All patients studied were within 24 hours of the onset of chest pain and on entry into study all were free of shock, heart block, bundle branch block, severe heart failure or an existing arrhythmia. By conventional monitoring, premature ventricular contractions were recognized in 64.5 percent of patients compared with 100 percent using the automated detection system (P <0.01). The corresponding percentages for recognition of premature atrial contractions were 45.2 vs. 96.8 percent (P < 0.001); serious ventricular arrhythmias, 16.1 vs. 93.5 percent (P <0.001); multifocal premature ventricular contractions, 6.5 vs. 87.1 percent (P < 0.001); and consecutive premature ventricular contractions, 13.0 vs. 77.5 percent (P < 0.001), respectively. The delay from the time of first occurrence as detected by the automated system to recognition by the conventional monitoring system averaged 18 hours for premature ventricular contractions, 10 hours for serious ventricular arrhythmias and 23 hours for premature atrial contractions. The on-line use of an automated arrhythmia detection system in the coronary care unit is suggested if further improvement in the elimination of arrhythmias as a primary cause of death after myocardial infarction is to be achieved. The presence of serious ventricular arrhythmias in virtually all patients after myocardial infarction suggests that prophylactic antiarrhythmic agents be used in this setting; however, none of the presently available antiarrhythmic agents have been shown to reduce mortality when given prophylactically following myocardial infarction.

Quinidine for Prophylaxis of Arrhythmias in Acute Myocardial Infarction

Abstract The efficacy of quinidine therapy for the prevention of cardiac arrhythmias was determined in a prospective controlled clinical trial involving 53 patients with uncomplicated acute myocardial infarction. After a loading procedure, 300 mg of quinidine sulfate or placebo was administered orally every six hours for five days under balanced, random, double-blind conditions. An automated arrhythmia detection system was used to quantify arrhythmias from stored continuous electrocardiographic tape recordings. By the sixth hour of therapy quinidine-treated patients demonstrated a 50 per cent reduction (p less than 0.001) in ventricular and supraventricular premature contractions, a 33 per cent lowered incidence (p less than 0.05) of serious ventricular arrhythmias and a blood quinidine level of 2.5 ± 0.3 (mean ± S.E.M.) mg per liter. One patient died in each treatment group. Mild adverse reactions to quinidine were observed in only two patients. Quinidine at a dosage producing modest blood concentration ...

Electrocardiographic and hemodynamic changes in experimental right ventricular infarction.

To investigate the electrocardiographic and hemodynamic changes in isolated right ventricular infarction, 0.25 ml or 0.5 ml of metallic mercury was injected into the right coronary artery of 14 closedchest dogs. At autopsy, at least 60% of the right ventricle was necrotic in every dog. Heniodynamic observations were made in 11 and electrocardiographic mapping was performed in all 14 dogs. Right atrial pressure rose in 10 and left atrial pressure in nine of the 11 dogs; early right atrial pressure did not exceed left atrial pressure, but late right atrial pressure was greater in four dogs. Although cardiac output and blood pressure fell significantly, circulation was maintained. Twelve of 14 dogs had transient ST-segment elevation in the right precordial leads, and 12 developed right bundle branch block. Abnormal Q waves or R waves of 1 mm or less appeared in the right precordial leads in 13 of the 14 dogs. Since right bundle branch block and abnormal Q waves in the right precordial leads have not been recognized as useful signs in human right ventricular infarction, further investigations are warranted to determine their value in clinical applications.

Unusual electrocardiographic manifestation of pulmonary embolism

Abstract A case of acute pulmonary embolism is presented because of its unusual electrocardiographic manifestation. The scalar ECG showed the transient development of abnormal Q waves with T-wave inversion in the precordial leads V 2 through V 5 . A simultaneous vectorcardiogram showed the initial forces to be directed to the right with a loss of the anterior forces. A thorough postmortem examination failed to reveal an acute myocardial infarction.

The vectorcardiogram and electrocardiogram in supravalvular aortic stenosis and coarctation of the aorta

Abstract VCGs were analyzed in 8 cases of isolated supravalvular aortic stenosis (SAS) and 21 patients with aortic coarctation. Seven of 8 patients with SAS and 10 with coarctation had a characteristic transverse plane QRS loop in which the maximum vector was directed rightward and posteriorly. It is postulated that in the absence of demonstrable right-sided lesions, this VCG pattern may, in some instances, reflect hypertrophy of the posterobasal portion of the left ventricle or a manifestation of left posterior hemiblock. An electro-vectorcardiographic diagnosis of right ventricular hypertrophy may be erroneously made in these patients.

Natural History of Cardiac Arrhythmias and their Prevention with Quinidine in Patients with Acute Coronary Insufficiency

In a prospective controlled clinical trial the natural history of cardiac arrhythmias and their prevention with prophylactic quinidine therapy were studied in 23 patients with acute coronary insufficiency without myocardial infarction. After a loading procedure, 300 mg of quinidine sulfate or placebo was administered orally every 6 hours for up to 5 days under balanced, random, double-blind conditions. An automated arrhythmia detection system was used to quantify arrhythmias from stored continuous electrocardiographic tape recordings.The frequency of ventricular and supraventricular arrhythmias tended to increase progressively on each successive day of study in placebo-treated patients. By contrast, in quinidine-treated patients all arrhythmias were quantitatively lower on each day of therapy and did not show a tendency toward progressive daily increases. In the placebo group there was an average of 140 premature ventricular contractions (PVCs) per day on the first day which increased to 600 PVCs per day by the fifth day, whereas with quinidine there was an average of 40 PVCs per day or less throughout the 5 days of study (P < 0.01). The daily increase in ventricular arrhythmias in placebo-treated patients with acute coronary insufficiency during the 5 days is in contrast to the natural history of patients with documented myocardial infarction who have a marked daily decrease in the frequency of ventricular arrhythmias during the first 5 days. Significant arrhythmia suppression with quinidine was present when mean blood quinidine concentration reached a steady state above 4 mg/liter at the end of the first day of therapy. Adverse reactions to quinidine were not observed. On the basis of these data, quinidine sulfate given prophylactically at a dosage producing modest blood concentrations appeared to be both effective and safe for the prevention of ventricular and supraventricular arrhythmias that occurred during the first 5 days after an episode of acute coronary insufficiency without infarction.

Computation of a variable location dipole representation from body surface leads

Abstract A computer method is described which permits the use of a variable location dipole rather than a fixed location dipole as the equivalent generator for the representation of the electrical activity of the heart. The following data are obtainable from digitized voltages of at least four or, preferably, as many independent leads as can be simultaneously recorded: 1. 1. The orthogonal components which define, at each digitized instant, the optimal spatial location of the single dipole. 2. 2. The orthogonal components which define, at each digitized instant, the optimal strength and direction of this dipole. 3. 3. The mean error involved in obtaining the best fit of the digitized voltages of the simultaneously recorded leads, and also the individual errors of each of these leads at each digitized instant of time.