Effects of different left ventricular load conditions on myocardial beta-adrenoceptor density in patients with rheumatic heart valvular disease.

1. The possibility that different left ventricular load conditions may influence myocardial beta-adrenoceptor function in various ways was evaluated by determining the receptor density in all four chambers of 69 patients with rheumatic heart valvular disease. 2. The left ventricular beta-adrenoceptor density was reduced by 44% in patients with left ventricular pressure overload (LVP), 66% in left ventricular volume overload (LVV), 56% in mixed volume and pressure overload (MOL), and 60% in those with no left ventricular pressure overload (NOL). Similarly, the right ventricular receptor density decreased significantly by 46%, 54%, 43%, and 46%, left atrial by 15%, 29%, 14%, and 21%; and right atrial by 27%, 30%, 28%, and 12% in LVP, LVV, MOL, and NOL, respectively. Thus, the general trend in the decrease in receptor density was LVV > MOL = NOL > LVP. 3. Furthermore, the LVV patients with the largest decrease in receptor density in all four chambers, similarly exhibited the largest ejection fractions (EF) and left ventricular internal diastolic and systolic diameters. 4. The results show that left ventricular volume overload is a major cause of attenuation in myocardial beta-adrenoceptor density, compared to other forms of ventricular overload in heart valvular disease. 5. Since elevated EF in volume overload patients is an indication of the severity of the disease, the decrease in their myocardial receptor density may be a reflection of the degree of influence of the disease on their sympathetic activity.