optimal PAEDP for this patient was 18 to 22 mm Hg and the cardiac output 4.5-5.0 liters/min. The patient survived and underwent resection of an akinetic area 4 months later. These studies indicate that hemodynamic monitoring in acute myocardial infarction is beneficial in the management of heart failure and shock. intubated. From the beginning of each experiment high speed, high frequency electrocardiographic leads II, Vi-V, and 3 intracardiac leads were recorded on magnetic tape. The intracardiac leads were recordings from the bundle of His and right bundle branch. Arterial blood gases and respiration were monitored. The dogs were allowed to breathe 1 of 3 aerosols, 2 of which used halogenated hydrocarbons as their propellants. Significant hypoxia or acidosis was not allowed to ocMicroscopy of Myocardium from the Left Ventricular Outflow Tract of Patients with Hypertrophic Obstructive Cardiomyopathy VICTOR J. FERRANS, MD, PhD; ANDREW J. MORROW, MD, FACC; WlLLlAM C. ROBERT’S, MD, FACC, Bethesda, Maryland Electron microscopic studies of surgically resected myocardium from the left ventricular outflow tract in 11 patients with hypertrophic obstructive cardiomyopathy (idiopathic hypertrophic subaortic stenosis) disclosed severe hypertrophy and focal interstitial fibrosis in each patient. The nuclei of the muscle cells were enlarged, with marginated chromatin, prominent nucleoli and bizarre infoldings of the nuclear membranes. The sarcoplasmic reticulum was normal in many areas, slightly dilated in others. Increased numbers of ribosomes, both free and attached to membranes of sarcoplasmic reticulum, were present in perinuclear zones. The amount of glycogen in muscle cells varied greatly. Many muscle cells showed abnormal orientation of myofibrils, some of which followed irregularly oblique courses through the cells. In all patients the Z bands of myofibrils frequently showed abnormalities characterized by increased width and by the formation of extensions of Z band material into adjacent regions of the sarcomeres. These Z band abnormalities were similar to, but less advanced than, those observed by Bishop in right ventricular myocardium after constriction of the pulmonary trunk. Basophilic degeneration of muscle cells was found by light microscopy in 2 patients ; in 1, electron microscopy showed that the basophilic deposits consisted of fibrils, 50 A in diameter, associated with granules 200 A in diameter. No evidence was observed to support Pearse’s concept that muscle cells in the hypertrophied outflow tract resemble those of atria1 myocardium or sinoatrial node. Cardiac Arrhythmias and Sudden Sniffing Deaths NANCY C. FLOWERS, MD, FACC; LEO G. HORAN, MD, FACC,