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This chapter assesses myocardial energetics. The heart requires very large amounts of energy, cycling many times its own weight in ATP daily, and uses a variable combination of carbohydrates, lipids, lactate, and amino acids as fuel. A key feature of the healthy heart is ‘metabolic flexibility’, i.e. the ability to use different substrates according to circumstances. As the syndrome of heart failure progresses, a steady downregulation of all aspects of cardiac metabolism may be seen. In extreme disease states, a fundamental deficiency in ATP can be demonstrated, but more subtle metabolic abnormalities are detectable at an earlier stage. Additionally, there are multiple downstream disturbances in mitochondrial function, in the high-energy phosphate pool and in excitation–contraction coupling. Ultimately, the detection of abnormalities of myocardial metabolism and energetics has spurred an interest in therapeutic modulation of metabolism in heart failure. This is attractive, as potentially such modulation would improve myocardial efficiency without the need for increased fuel delivery. Such therapies could have an additive effect to current heart failure management which generally relies on correction of the maladaptive neurohumoral consequences of the heart failure syndrome.

This chapter covers all areas of pacemaker programming and choices related to pacing. Methods of choosing rate limits, and related programming features are described for the lower rate interval, the upper rate interval, the atrioventricular interval, and refractory and blanking periods are described in detail. The anatomical and signal changes for each period are defined, and all descriptions are illustrated with example ECGs to show different programme outcomes. Rate response, programming rate response, and mode switching are covered. Automated functions and stored information are described, and algorithms to prevent atrial arrhythmias are explained. Finally, pacemaker-mediated tachycardia is outlined, including detection and methods of terminating the pacemaker-mediated tachycardia (PMT).