Myocardial oxygen supply in left ventricular hypertrophy and coronary heart disease.

Coronary arteriolar dilation adjusts blood flow according to local fluctuating metabolic needs of the myocardium. Because of high extravascular compression during systole, the subendocardial layer of the left ventricle is especially dependent on the duration and the perfusion pressure of the diastolic period. In patients with obstructive coronary artery disease, regional arteriolar dilation is utilized to compensate for focal arterial stenoses. Coronary blood flow may be compensated with the patient at rest, but loss of reserve arteriolar dilation limits further adjustment to superimposed transient increases in metabolic needs. Subendocardial perfusion in the region supplied by the stenosed artery is especially vulnerable to shortened diastolic time during tachycardia. In patients with chronic aortic valve disease, the metabolic rate of the left ventricle is increased in proportion to the increases in myocardial mass and work. Coronary blood flow and metabolic rate per gram of the hypertrophied myocardium are normal when the patient is at rest, at the expense of diminished coronary arteriolar reserve. High tissue pressure relative to the diastolic perfusion pressure probably contributes to the diffuse subendocardial ischemia that occurs in these patients during tachycardia.

Acute electrophysiologic effects of nadolol.

The acute effects of intravenous nadolol (0.01 and 0.02 mg/kg) on cardiac electrophysiologic parameters were assessed with His bundle recording and programmed atrial stimulation. The higher dose of nadolol reduced resting heart rate (71 vs. 65 beats/min, P less than 0.02), and the degree of slowing was related to the initial heart rate (r = -0.68, P less than 0.05). Atrioventricular conduction time as defined by the paced A-H interval, rose by 12 msec (P less than 0.001) after nadolol (0.02 mg/kg) administration. Atrial refractoriness increased (by 10 msec, P less than 0.02) only at the higher dose level with nadolol. At both dose levels, atrioventricular nodal effective and functional refractory periods were increased (P less than 0.02) by a mean of 45 and 21 msec, respectively, suggesting greater sensitivity of atrioventricular nodal refractoriness to beta-adrenergic blockade. Nadolol's effects were generally similar to those of previously reported studies with other beta-adrenergic blockers. These data suggest that nadolol slows conduction through the atrioventricular node and increases atrial and atrioventricular nodal refractoriness.

Two dimensional echocardiographic similarity of Fabry's disease to cardiac amyloidosis: a function of ultrastructural analogy?

A 53-year-old man with Fabry's disease was studied by echocardiography. Both M-mode and two dimensional echocardiographic examinations produced findings indistinguishable from those previously described as virtually diagnostic of cardiac amyloidosis. Possible causes for the "granular sparkling" appearance and clinical implications of the similarities were discussed.

Acute coronary insufficiency - coronary occlusion after intermittent ischemic attacks.

We used angiography in a prospective study of the coronary circulation in patients with acute coronary insufficiency. Reversible ST-T changes during the acute illness corresponded anatomically with severely narrowed coronary arteries (80 to 95 per cent stenosis). Angiograms repeated four months later showed new complete occlusions in nine of 30 severely stenotic arteries. Eight of the new occlusions occurred in severely narrowed arteries previously correlated with regional ST-T changes. Six patients had myocardial infarctions, five of which corresponded with the site of a new occlusion. These results provide indirect evidence that the acute coronary-insufficiency syndrome commonly represents intermittent transient coronary-artery occlusion and a threat of new permanent occlusion of the same artery. Myocardial infarction in these patients appeared to occur as a complication of the new occlusion.