Paradoxic improvement in regional wall motion during high-dose dobutamine stress echocardiography. A marker for hibernating myocardium?

Dobutamine stress echocardiography detects myocardial ischemia by inducing regional left ventricular systolic dysfunction. Augmentation of wall motion in hypokinetic segments has also been noted with low-dose dobutamine, suggesting myocardial viability. We report a case of regional ventricular improvement during high-dose dobutamine therapy, which may represent relief from myocardial hibernation or changes in regional loading conditions.

Aortic valve stenosis. Management in children and adults.

Aortic valve stenosis may be congenital or acquired. Medical management includes advice to avoid heavy physical effort, prevention of infective endocarditis, use of digitalis and diuretics for cardiac failure, and preservation of atrial systole. When operation is necessary, open aortic valve commissurotomy is preferred in children and replacement of the valve is preferred in adults. Women of childbearing age should use conventional barrier contraceptives, and those with severe stenosis should have valve replacement before becoming pregnant. Aortic valvuloplasty, particularly in adults, is only of temporary benefit.

Patent foramen ovale associated with platypnea and orthodeoxia.

A case of positionally symptomatic right-to-left shunting across a patent foramen ovale with both platypnea and orthodeoxia despite normal pulmonary arterial pressures and normal right ventricular function is documented. When the patient was in a supine position, the calculated right-to-left shunt was 12.8 percent, and when seated 25 percent. Surgical closure of the patent foramen ovale relieved the symptoms and positionally induced shunting. The prevalence and associations of permanent and intermittent patency of the foramen ovale are discussed. It is recommended that those at risk of thromboembolism be screened for patency by contrast ultrasound or color flow techniques. If present, surgical closure needs to be considered to prevent paradoximal embolism and stroke.

Planar positron imaging of rubidium-82 for myocardial infarction: a comparison with thallium-201 and regional wall motion.

Rubidium-82 (Rb-82) is a generator-produced, short half-life (76 seconds) positron emitting potassium analog. Using a mobile gamma camera equipped with a rotating tungsten collimator and high-energy shielding, we examined the use of Rb-82 in the coronary care unit and clinical laboratory for detection of perfusion defects due to myocardial infarction. We studied 31 subjects, 10 patients with acute myocardial infarction, 12 with remote myocardial infarction, and nine controls. Rb-82 images were compared with Tl-201 and regional wall motion for detection of infarct-related arteries. Of the 22 patients with myocardial infarction, 16 were identified with Rb-82 and Tl-201. In nine control subjects, eight were normal with each method. Correlation between Rb-82 and Tl-201 defect scores was excellent. Sensitivity and specificity for infarct-related arteries were similar for Rb-82, Tl-201, and wall motion imaging. Thus planar Rb-82 imaging can detect MI reliably in the coronary care unit and in the clinical laboratory.

Silent myocardial ischemia: therapeutic implications.

Current concepts concerning the pathophysiology of acute myocardial ischemia are reviewed. The importance of intermittent, dynamic shifts in the diameter of the coronary artery lumen is emphasized. Traditionally, it has been thought that angina pectoris is the common clinical hallmark of myocardial ischemia. It is now apparent that asymptomatic episodes of myocardial ischemia may be occurring far more frequently than symptomatic episodes. Although the natural history of asymptomatic myocardial ischemia is still unknown, ischemia, even in an asymptomatic form, can have serious consequences. This suggests the need for a careful assessment of patients in whom ischemia has been detected. In truly asymptomatic patients, detection is usually fortuitous; in patients with known coronary arterial disease, asymptomatic episodes should be sought as part of a noninvasive cardiac investigation, using multiple-stage exercise treadmill testing and 24-hour ambulatory electrocardiographic monitoring. Suggestions are made for the management of asymptomatic myocardial ischemia in relation to three patient groups: (1) asymptomatic ischemia in patients known to have symptomatic ischemia as well, (2) asymptomatic ischemia in patients without symptoms at any time, and (3) asymptomatic ischemia in patients who have had myocardial infarction. Medical management includes the use of calcium channel blocking drugs, beta-adrenergic blocking drugs, and nitrates. Documentation of an inadequate coronary artery reserve or evidence of associated left main coronary artery disease indicates the need for either aortocoronary bypass graft surgery or percutaneous transluminal coronary angioplasty, depending on the condition of the coronary anatomy and the degree of ventricular function. Whatever mode of treatment is used, documentation of its effectiveness should always be determined by appropriate follow-up studies. Clinical studies of the natural history of asymptomatic myocardial ischemia and its management are urgently needed.

Current use of myocardial protection during coronary artery bypass surgery: results of a survey.

The literature suggests that certain methods of myocardial protection employed during coronary artery bypass graft (CABG) surgery may significantly affect postoperative recovery. A retrospective study comparing the use of different cardioplegia solutions during CABG surgery at our institution failed to show significant differences in perioperative ischemic events or in patient survival. A subsequent survey was conducted among 140 surgeons worldwide to determine the influence of myocardial protection on perioperative ischemic events and patient survival.