Pentaerythritol trinitrate and glyceryl trinitrate on myocardial oxygen consumption and haemodynamics in the dog

1. The effects of pentaerythritol trinitrate (pentrinitrol) and glyceryl trinitrate on myocardial oxygen consumption and myocardial and systemic haemodynamics were studied in anaesthetized open-chest dogs. An in vivo oximeter in the coronary sinus permitted continuous determination of arteriovenous oxygen difference and myocardial oxygen consumption. All parameters were determined simultaneously at various intervals after drug administration. 2. Myocardial oxygen consumption was diminished by both nitrates for more than 16 min. Changes in arteriovenous oxygen difference and coronary sinus oxygen content were variable between drugs. Following an initial transient increase, coronary blood flow was reduced by both nitrates. Aortic blood pressure, aortic blood flow, left ventricular end-diastolic pressure and left ventricular dP/dt were also reduced. Heart rate and contractile force were not appreciably altered by either nitrate. 3. The decrease in myocardial oxygen consumption appears to be associated with the haemodynamic profile of these drugs. Both nitrates produced comparable reductions in preload (left ventricular end-diastolic pressure) and afterload (aortic pressure) as well as dP/dt.