Michael G. Baird

Significance of reciprocal S-T segment depression in anterior precordial leads in acute inferior myocardial infarction: Concomitant left anterior descending coronary artery disease?

Abstract The reciprocal changes of S-T segment depression in the anterior precordial leads of the electrocardiogram in acute inferior myocardial infarction may be due to left anterior descending coronary artery disease and anterior wall ischemia. The electrocardiograms of 45 patients with acute inferior infarction who had subsequent cardiac catheterization (41 patients) or necropsy (4 patients) were examined to test this hypothesis. Significant left anterior descending coronary artery disease (greater than 70 percent stenosis of luminal diameter) was observed in 31 (69 percent) of the 45 patients. The sensitivity, specificity and predictive value of S-T depression (1 mm or greater) in various anterior precordial leads singly or in combination was determined for this lesion. Left anterior descending coronary artery disease was present in 23 of 24 patients with S-T depression in one or more leads from V 1 to V 4 (predictive value 95 percent), and this index had the best combination of sensitivity (74 percent), specificity (93 percent) and predictive value in this group. Seven of 13 patients with left anterior descending coronary artery disease had S-T depression only in lead I or aVL, or both (sensitivity 100 percent, specificity 53 percent and predictive value 54 percent). S-T depression in any of leads I, aVL and V 1 to V 6 occurred in 37 patients, and 31 of these had left anterior descending coronary artery disease (sensitivity 100 percent, specificity 57 percent and predictive value 84 percent). The eight patients without anterior precordial lead S-T depression did not have left anterior descending coronary artery disease. Complications of infarction developed in 13 patients;S-T depression in at least one of leads V 1 to V 4 occurred in 12 (92 percent) of these 13 but in only 12 (38 percent) of 32 patients without complications. Thus the predictive value of S-T depression in leads V 1 to V 4 (95 percent) for left anterior descending coronary artery disease is greater than the occurrence of the latter (69 percent) in all cases of acute inferior myocardial infarction (p

Comparison of Clinical and Treadmill Variables for the Prediction of Outcome After Myocardial Infarction

To assess the relative prognostic merits of 15 clinical and 10 predischarge exercise test variables, 226 patients who had sustained an acute myocardial infarction were studied. A submaximal treadmill test was performed on 205 patients to a mean work load of 5.7 +/- 2.9 METS. Testing was performed an average of 11.7 (range 6 to 33) days after myocardial infarction. During the first year of observation, major cardiac events were noted in 33 patients (16%), unstable angina in 7 (3.4%), recurrent myocardial infarction in 14 (6.8%) and death in 12 patients (5.9%). Cardiac mortality correlated with mean peak serum creatine kinase (CK) (p less than 0.05), history of previous myocardial infarction (p less than 0.01) and ST segment depression at rest (p less than 0.01). The only exercise variable that correlated with cardiac mortality was poor exercise endurance (p less than 0.05). Multivariate risk stratification of clinical and treadmill variables from these 205 patients using linear discriminant analysis produced a function that correctly classified 95% of those who were event-free and 80% of those who died. The first four discriminant variables that contributed independent information for the prediction of cardiac mortality were: 1) ST segment depression at rest; 2) CK greater than 1,280 IU/liter; 3) exercise duration less than 3 minutes; and 4) a history of previous myocardial infarction. ST segment depression on the predischarge treadmill test did not predict any event, nor did it improve the predictive accuracy of the clinical variables. It is concluded that a history of previous myocardial infarction and ST segment depression on the rest electrocardiogram indicate a poor prognosis after acute myocardial infarction. Poor endurance is the only exercise variable that suggests a future cardiac event. Prognosis after acute myocardial infarction is more accurately predicted by these clinical data than by variables derived from the predischarge treadmill test.

Complications of Transesophageal Echocardiography in Ambulatory Adult Patients: Analysis of 1500 Consecutive Examinations

Transesophageal echocardiography is a new approach that can be used to image cardiac structures. It combines two existing technologies: cardiac ultrasound and endoscopy. To obtain a cardiac image, the transesophageal probe has to be positioned properly within the esophagus. The first 1500 consecutive transesophageal echocardiographic examinations in ambulatory adult patients from one center were analyzed to identify conditions associated with failed esophageal intubation and procedural complications. Esophageal intubation was not achieved in 11 patients (0.73%). The reasons for the failure of intubation were operator inexperience, hypersensitive pharynx despite topical anesthesia, and cervical spondylosis. Six of those patients also had a history of dysphagia. Procedural complications were identified in seven patients (0.47%). Tracheal intubation was present in four patients, with immediate development of stridor and incessant cough in two patients. Atrial fibrillation developed in two patients--one had atrial myxoma and one had mitral stenosis. Bronchospasm developed during the transesophageal examination in one patient who was receiving long-term treatment for bronchial asthma. We conclude that transesophageal echocardiography is feasible in most adult patients in the ambulatory setting and that the complication rate is very low. Proper patient selection and preparation are crucial to the successful performance of this procedure.

Role of Transesophageal Echocardiography in Percutaneous Balloon Mitral Valvuloplasty

Echocardiography is useful in the selection of patients for percutaneous balloon mitral valuuloplasty, which is an effective treatment in suitable patients with rheumatic mitral stenosis. Transesophageal echocardiography appears superior to precordial echocardiography in this role because transesophageal echocardiography is not only reliable in the assessment of mitral valvular morphology but also more sensitive in the detection of left atrial thrombi and mitral regurgitation. Transesophageal echocardiography can be used in guiding the proper positioning of the catheters during the dilatation procedure. Complications of balloon mitral valvuloplasty such as torn mitral leaflets or atrial septal defects can also be diagnosed reliably by transesophageal echocardiography. Thus, transesophageal echocardiography should be an integral part of balloon mitral valvuloplasty.

Three-month efficacy and safety of once-daily diltiazem in chronic stable angina pectoris

The 3-month efficacy and safety of a once-daily controlled formulation of diltiazem (180 to 360 mg/day) were assessed in a study of 54 patients with angina pectoris. This multicenter study was a nonrandomized, placebo run-in, open-label, 3-month trial followed by a 1-week, double-blind, randomized period during which most patients (89%) received placebo. There were only minimal changes in the time to termination (mean change +/- SEM -5.8 +/- 9.6 seconds), time to onset of angina (10.5 +/- 12.2 seconds), and the time to 1 mm ST-segment depression (2.9 +/- 12.5 seconds) from the end of the titration phase to the end of the open-label study. There were, however, statistically significant differences between the end of the 3-month treatment phase and the end of the 1-week randomized placebo phase for those 3 efficacy parameters (-37.3 +/- 11.2, -58.6 +/- 13.6, and -45.6 +/- 16.4 seconds, respectively). Diltiazem significantly decreased the frequency of anginal attacks and nitroglycerin use at the end of the 3-month treatment phase compared with results at the end of the randomized double-blind placebo phase. No new or unusual adverse events were reported during treatment. The present results suggest that there is no loss of efficacy of once-a-day diltiazem when administered for a long period to patients with chronic stable angina pectoris.

Role of diltiazem in the treatment of silent myocardial ischemia.

Silent myocardial ischemia is a frequent finding when Holter monitoring is done in patients with advanced coronary disease. Silent ischemia is associated with a worse prognosis in patients with stable or unstable angina, survivors of myocardial infarction, and populations at risk for coronary disease. Whether medical therapy for silent ischemia improves prognosis is not known. In a randomized, placebo-controlled, multicenter trial of 60 patients with documented coronary disease, positive exercise tests, and ischemic episodes on Holter monitoring, long-acting diltiazem reduced ischemic episodes by 50% compared to placebo, from a mean of 5.6 to 2.8 p < 0.0001). Efficacy was maintained over 24 h and diltiazem also significantly improved exercise test parameters. Three smaller studies also demonstrated that diltiazem effectively reduces ambulatory ischemia: however, results with nifedipine are conflicting, with several studies showing no benefit. In contrast, β-blockers reliably reduce ischemic episodes. The role of medical therapy for silent ischemia will be clarified only when its effect upon morbidity and mortality are determined.