Real Time Modulation of End Diastolic Volume as a Novel Therapy for Dilated Cardiomyopathy and Congestive Heart Failure
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abstract
Congestive heart failure (CHF) is a major public health issue in the developed and developing world. In the U.S., CHF affects more than 5.3 million people with 550,000 new cases diagnosed each year. Approximately 20 percent of hospitalizations are due to acute CHF, incurring a health-care system cost of $34.4 billion. Heart failure has two main forms: systolic dysfunction and diastolic dysfunction. Many patients with heart failure have both types of dysfunction. Though systolic heart failure is more commonly mentioned, there is growing recognition that CHF caused by a predominant abnormality in diastolic mechanics (filling and relaxation) causes significant morbidity and mortality. In patients with systolic heart failure, there are abnormalities in the pressure-volume relationship during systole that includes decreased ejection fraction (EF), stroke volume, and stroke work. In patients with isolated diastolic heart failure, the only abnormality in the pressure-volume relationship occurs during diastole, when there are increased diastolic pressures with normal diastolic volumes. Whereas the diastolic pressure-volume relationship may reflect a more compliant chamber, increased diastolic pressure and abnormal relaxation reflect the presence of abnormal diastolic function. Therefore, patients with symptomatic heart failure have abnormalities in diastolic function, those with a normal EF have isolated diastolic heart failure, and those with a decreased EF have combined systolic and diastolic heart failure. Thus a critical gap in present device solutions to CHF is a single device that can address concurrently reduction of LV chamber dimensions (remodeling) and also improve and not impede LV filling by lowering the filling pressure (i.e. without impeding diastolic function). The biphasic support and recoil device technology investigated in this dissertation would provide a means for guided intervention whereby normal growth and remodeling processes are directed toward a gradual reduction in size in systolic dysfunction and enhanced ventricular filling using diastolic recoil properties of the device. In this dissertation prototyping and testing of a novel minimally invasive cardiac device technology is presented. Our tests indicate that this technology has the necessary mechanical actions to enable the integration of therapy for systolic and diastolic dysfunction in two principal ways (1) adjustable passive cardiac support or progressive constraint to facilitate the gradual reduction in size of dilated, diseased hearts, thereby improving pumping efficiency; (2) diastolic recoil technology with the ability to transfer energy from systolic contraction to diastolic filling, which may potentially reduce ventricular filling pressures, without compromising ventricular systolic function.
