Background There are significant limitations in the current approaches to assessing 2 important areas of cardiovascular physiology - the systemic circulation and left ventricular (LV) performance. The investigators' have repurposed the concepts of systemic vascular conductance to assess systemic circulation, and the head capacity principle to assess LV performance. The investigators' now seek to test these concepts in human adults, with heart failure and without heart failure, using non-invasive methods. Hypothesis There will be a depressed head-capacity curve and reduced power among patients with heart failure which will indicate compromised left ventricular pump function. Methods The research study will involve a single outpatient visit per subject. The study will take place with the subject supine on a bed/table. The subjects will be instrumented with EKG electrodes and finger blood pressure cuffs. The continuous finger BP device performs a waveform analysis in real-time to determine the non-invasive stroke volume, cardiac output, and blood pressure. The patient will be supine for at least 5 minutes to collect baseline data before being handed a dynamometer device. The subject will then be asked to squeeze the dynamometer with maximum force for a minimum of 2 minutes while only engaging their forearm and remaining relaxed in the rest of their body. The subject will then release the dynamometer and remain supine, in recovery, for a minimum of 5 minutes. Following the handgrip test, the instrumentation will be removed and the patient's participation in the study will be complete. The study duration should be about 20 min.