Circulation
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Failure of the pulse pressure to increase in the post-premature beat is considered characteristic of idiopathic hypertrophic subaortic stenosis (IHSS). The sensitivity and specificity of this response were compared to the change in left ventricular ejection time (LVET) in 12 patients with IHSS, in ten control patients with valvular aortic stenosis (AS) and in five normal subjects. The post-PVC pulse pressure increased in all normals and in nine of the ten patients with AS. ⋯ A positive Brockenbrough sign was seen in only 33%. On the other hand, LVET increased greater than 20 msec in eleven of twelve patients with IHSS, whereas all normal subjects and all patients with AS showed either decreases in LVET or increases smaller than 20 msec. Prolongation of the LVET during the post-PVC beat greater than 20 msec appears, therefore, to be a more sensitive sign of IHSS than the corresponding change in pulse pressure.
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A portable radioisotopic technique was developed to demonstrate cerebral circulatory deficit, as part of a collaborative study to define and diagnose cerebral death simply and rapidly, in comatose, apneic patients with electrocerebral silence. The method involves an intravenous injection of 2mCi of 99mTcO4, and recording time/activity curves over the cranial cavity and a femoral artery simultaneously, using twin probe radioisotope detector equipment. Eight comatose, apneic patients had 142 studies in conjunction with clinical electroencephalographic and other laboratory evaluations. ⋯ A normal bolus tracing should be simultaneously observed over a femoral artery and this is used as a control. The method is safe and simple and offers significant information about the irreversibility of cerebral blood flow. Although further studies are indicated, the method appears to be most promising as a fundamental bedside laboratory test in the diagnosis of cerebral death in conjunction with other clinical and laboratory criteria.
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Electrophysiological studies with atrial extrastimulus technique suggested the presence of dual atrioventricular (A-V) nodal pathways in a patient with hypothyroidism, as evidenced by a sudden increase of H1-H2 intervals at critical A1-A2 coupling intervals. Following the atrial extrastimulus (A2), a third impulse (A3) occurred spontaneously. During slow pathway conduction of A2, and A3, appearing at a critically timed interval allowed fast pathway conduction, resulting in an earlier than expected QRS (a form of supernormal conduction). This demonstration of fast pathway conduction during slow pathway conduction adds strong evidence for the existence of dual A-V nodal pathways.
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Although hemodynamic benefit has been shown with sodium nitroprusside (NP) in acute coronary pump failure, complete understanding of the mechanisms of action of the agent on the cardiocirculation and its value in chronic ventricular dysfunction are lacking. This investigation evaluates the effects of NP on the systemic and regional arterial and venous beds and on cardiac dynamics, ventricular volumes, contractile state and myocardial energetics in long-standing congestive heart failure. Twelve patients with chronic coronary pump dysfunction received NP infusion to lower systolic pressure to 95-105 mm Hg. ⋯ Depressed stroke index (SI) and cardiac index (CI) increased (P less than 0.05) with NP: despite the fall in LVEDP, when ventricular filling pressures with the agent were at levels slightly above normal. Dextran infusion given with NP to restore LVEDP to moderately elevated values increased SI and CI (P less than 0.05) when NP alone produced no change in stroke output. Thus, the peripheral vasodilator properties of nitroprusside improve LV function by reducing impedance to ventricular ejection, while MVO2 is diminished by decreasing LV preload and afterload through relaxing actions