Background-The decay of the pressure gradient across a stenotic mitral valve is determined by the size of the orifice and net AV compliance (C n ). We have observed a group of symptomatic patients, usually in sinus rhythm, characterized by pulmonary hypertension (particularly during exercise) despite a relatively large mitral valve area by pressure half-time. We speculated that this discrepancy was due to low atrial compliance causing both pulmonary hypertension and a steep decay of the transmitral pressure gradient despite significant stenosis. We therefore tested the hypothesis that C n is an important physiological determinant of pulmonary artery pressure at rest and during exercise in mitral stenosis. Methods and Results-Twenty patients with mitral stenosis were examined by Doppler echocardiography. C n , calculated from the ratio of effective mitral valve area (continuity equation) and the E-wave downslope, ranged from 1.7 to 8.1 mL/mm Hg. Systolic pulmonary artery pressure (PAP) increased from 43Ϯ12 mm Hg at rest to 71Ϯ23 mm Hg (range, 40 to 110 mm Hg) during exercise. There was a particularly close correlation between C n and exercise PAP (rϭϪ0.85).Patients with a low compliance were more symptomatic (PϽ0.025). Catheter-and Doppler-derived values for C n , determined in 10 cases, correlated well (rϭ0.79). Conclusions-C n , which can be noninvasively assessed, is an important physiological determinant of PAP in mitral stenosis. Patients with low C n represent an important clinical entity, with symptoms corresponding to severe increases in PAP during stress echocardiography.
Absence of early ST segment elevation resolution after angiographically successful primary PTCA identifies patients who are less likely to benefit from the early restoration of flow in the IRA, probably because of microvascular damage and subsequently less myocardial salvage.
The time course of ventricular arrhythmias in the early period (0--30 minutes) after ligation of the left anterior descending coronary artery was studied in 41 open-chest mongrel dogs anesthetized with pentobarbital sodium (Nembutal). ECGs and seven single and composite electrograms from various regions in and around the ischemic zone were recorded throughout the experiments. Two periods of ventricular arrhythmias were clearly seen. The first occurred 2--10 minutes after coronary ligation, peaking at 5--6 minutes, and was designated as immediate ventricular arrhythmias (IVAs). There was a distinct correlation between incidence, severity, onset and termination of IVA and the degree of local delay and fragmentation of the normal sinus activation spread in the ischemic subepicardial zone. The second wave of ventricular arrhythmias occurred 12--30 minutes after ligation independently of the previous increased delay and fragmentation of activation in the ischemic subepicardium. Delayed ventricular arrhythmias (DVAs) were as severe as IVAs--there were nine instances of ventricular fibrillation during DVA and seven during IVA. While the mechanism of IVA is most probably related to reentry accompanied by delay and fragmentation of ischemic subepicardial activation, the mechanism of DVA remains unclear. Our evidence suggests that DVAs are also reentrant, with the reentry pathways located in deep myocardial structures or involving microscopic pathways at the Purkinje muscle junction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.