Protein nutrition, immune responsiveness and experimental atherosclerosis

For technical reasons it has not been possible previously to record arterial blood pressure and ST segment shift simultaneously and with accuracy in freely ambulant subjects. Therefore, data on haemodynamic changes occurring during angina have been limited to the bedside or the laboratory. A new system has been developed which utilizes a frequency-modulated tape recorder enabling accurate reproduction of the ECG signal and embodies the capacity to record intra-arterial pressure using a transducer perfusion unit conventionally used to study hypertensive subjects. Validation experiments have been conducted which document the system's frequency response, linearity, signal to noise ratio, temperature stability and also the effect of battery depletion. Analysis of data involved three stages. Simultaneous analog trend plots of arterial pressure, heart rate and ST segment allowed visual representation of individual patient data. Two systems were developed for digital analysis; the first was semi-automated and involved manual blood pressure analysis; the second was totally automated. Clinical evaluation was performed on 22 patients with arteriographically proven severe coronary artery disease who suffered frequent attacks of angina. Control data from quantitated isometric and dynamic exercise in the laboratory were used to compare and contrast the effects of normal daily activities outside the hospital and to test the hypothesis that double product (heart rate + systolic pressure) has any relevance in such patients. The most important finding was that both angina and r.symptomatic episodes of ST segment depression were almost invariably accompanied by an increase in heart rate, whereas there was a marked scatter of blood pressure changes ranging from an increase to a substantial fall. Double product was not reproducible during angina and it is suggested that, as the blood pressure response is complex, double product is inappropriate in its present form and, if used at all, heart rate and systolic blood pressure should not have equal weighting.