Post-partum hemodynamics in mitral insufficiency.

To the Editor: In their article outlining potential consequences of postpartum hemodynamics in mitral insufficiency, Khanlou et al (1) rightly underscored the importance of puerperal increases in systemic vascular resistance (SVR). Their patient experienced difficulties on postpartum Day 7, including an increase in SVR associated with increased mitral valve regurgitation, left atrial enlargement, and pulmonary venous congestion. Their patient responded rapidly to diuresis and supportive care.

The mechanisms of puerperal hemodynamics cannot so simply be attributed to an isolated increase in SVR, however. Concomitant with, and a major contributing factor to, this increase is a major reduction in uterine blood flow secondary to myometrial contraction and resultant increased local vascular resistance, with redirection of residual excess blood volume to other central locations.

In addition, a rapid drop in oncotic pressure from centralization of extravascular fluids and dilution of remaining albumin concentrations can result in early appearance (within minutes to hours) of a disruption in alveolar fluid reabsorption and, with increased pulmonary venous pressure engendered by mitral insufficiency, a significant risk of pulmonary edema. Although this relatively immediate impact was not observed in this patient, data regarding her oncotic pressure were not provided. The authors correctly excluded postpartum cardiomyopathy from consideration in connection with this result, although the timing of the clinical presentation normally would have included this possibility in the admission differential diagnosis.

In patients with cardiac risk conditions, all of the above factors must be kept in mind. This would be of especial interest in patients with other conditions, such as pregnancy-induced hypertension resulting in increased SVR augmented by endogenous or exogenous volume expansion, especially with compromised oncotic status as a result of chronic, marked proteinuria and diminished synthesis of albumin in favor of other polypeptide priorities.

Reference

(1.) Khanlou H, Khanlou N, Eiger G. Relationship between mitral valve regurgitant flow and peripartum change in systemic vascular resistance. South Med J 2003;96:308-309.

Richard P. Perkins, MD

Fort Lauderdale Perinatal Associates

Fort Lauderdale, FL