Systolic time intervals during spironolactone treatment of digitalized and non-digitalized patients with ischaemic heart disease.

The effect of spironolactone on cardiac contractility indices was studied by externally recording systolic time intervals in four digitalized and four non-digitalized patients with ischaemic heart disease. A negative inotropic effect was found after spironolactone 100mg b.i.d. in all eight patients, as measured by an increase in pre-ejection period index PEPI (p less than 0.01), and the ratio between pre-ejection period and left ventricular ejection time PEP/LVET (p less than 0.001), while pre- and afterload remained constant. As expected, digoxin exerted a positive inotropic effect, as a decrease was observed in PEPI (p less than 0.01), and PEP/LVET (p less than 0.001). It was not possible to ascertain whether the observed effect was caused by a pharmacological interaction at receptor level between spironolactone and digoxin, or indirectly to changes in endogenous substances e.g. aldosterone. The results suggest that spironolactone may have unintended side effects in patients with severe heart failure and that its use be reevaluated.