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KMID : 0378019810240010085
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New Medical Journal
1981 Volume.24 No. 1 p.85 ~ p.99
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Hemodynamic assessment of mitral stenosis and right ventricular performance
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Abstract
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The cardiac performance is regulated by the integration of preload, afterload, contractility (inotropism), heart rate and synergy of ventricular contraction, the major determinants of which govern the stroke volume and cardiac output. The preload is the ventricular end-diastolic circumferential fiber length as determined by the diastolic blood volume, and ventricular end-diastolic pressure. The afterload is the impedence offered to ventricular systolic emptying, and arterial resistance.
The contractile or inotropic state of the myocardium can be defined as the quality of ventricular performance at a given loading conditions (preload and afterload), heart rate and ventricular synergy. Two principal assessments to study of cardiac contractility are used in terms of the pump performance and the muscle performance of the ventricle.
Valvular heart disease may be considered to impose two different types of stress on the cardiac chamber proximal to the lesion. There are either pressure overload (increased afterload) or volume overload (increased preload). The compensatory mechanism of the pressure overload and volume overload offer to hypertrophy and dilatation of the chamber. Hypertrophy, increased muscle mass, call upon the development of greater systolic force. Dilatation, overfilled chamber volume, enables increased strength and extent of shortening by Frank-Starling´s mechnism.
These mechanisms preserve the systemic circulation at the cost of increased myocardial ,oxygen needs and elevated ventricular filling pressures. In these view, we shall discuss the hemodynamic parameters; cardiac output, stroke volume, ventricular end-diastolic pressure, mitral valve gradient and pulmonary circulation, and right ventricular performance observed in 18 cases of pure mitral stenosis (of 37 cases, mitral stenoinsufficiency) which were conformed during the left ventricular angiography (no regurgitant jet) at the cardiac catheterization and at the fields of operative findings. The result obtained in 18 cases of mitral stenosis were as following:
1. Cardiac index of mitral stenosis was average 2.65L/min/m2 and 2.54 L/min/m2 in 15 cases less than 1 cm´ of mitral valve area, which seemed the cardiac output to be maintained at the lower normal range in response to elevated ventricular filling pressure at the proximal to the leson of mitral obstruction.
2. The mean left ventricular end-diastolic pressure elevated more than 0-12mmHg observed in 6 cases, and whose functional class was in III or more.
3:. Tl e systolic time intervals, as hemodynamic pump- parameter, were measured and the mean time of QS2 was 377 msec (p.393±14), the mean of LVET was 272 msec (p.291± 10) and the mean of PEP was 105 msec (p.,102±103). The PEP/LVET was 0.387, however, in 2 cases of congestive heart failure the PEP/LVET was increased more than 0.44.
4. At the mitral valve orifice area less than 1cm2 and the clinical stage 11(14 of 18 cases), the pulmonary vascular resistance (PVR) were within 400 to 500 dyne-sec-cm-5, and increasirgg pulmonary vascular resistance more than 400 dyne-sec-cm5, the clinical stage became increased rapidly.
5. At the mitral valve area less than 1 cm2, the mean MVG was 17.3mmHg, the mean PVR, 568 dyne-sec-cm-1 and RV systolic mean 72mmHg and RV end-diastolic pressure, 11.2mmHg respectively. The rate of RV pressure development at the isovolumic contraction time (peak dp/dt) was within 244-847mmHg/sec (av, 571mmHg/sec) in respect to MVA less than 1 cm2.
6. The mean right ventricular end-diastolic pressure more than 0-8mml-Ig observed in 11 cases (61%) of mitral stenosis, over than II-III of clinical stages.
7, Tricuspid regurgitation associated with mitral stenosis observed in 5 cases (27.8%) of all. 4 cases of them were functional tricuspid incompetence, 1 case was organic tricuspid incompetence and 3 cases of all required tricuspid annuloplasty. These hemodynamic parameters associated mitral stenosis obtained that the mean RV peak dp/dt was 659 mmHg/sec, the mean RV peak systolic pressure was 77mmHg, the mean PA pressure was 51mmHg and the RA mean pressure was 11mmHg.
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