E_Stethoscope : Portable Digital Auscultation Based on Wireless Sensor Node to Diagnose Diastolic Dysfunction in Hypertensive Heart Disease

Study proposal aims to look into treatment of hypertension (HT) and its complications of the exact high healthcare costs. In 2004, Singapore adult prevalence of hypertension was 20.1%. World Health Organization estimates that HT causes 4.5% of global disease burden, and that 62% of cerebrovascular disease and 49% of ischemic heart disease are attributable to suboptimal blood pressure (BP) control.

Recently, scrutiny has been focused on appropriate BP levels at which to initiate HT treatment with the benefit of strict BP targets in otherwise uncomplicated HT is questioned, as HT drug treatment is not without risks. This underscores the need to stratify hypertension patients according to target organ damage, so that affected HT patients may be selected for intensive BP lowering.

Hypertensive heart disease (HHD) is a heart condition that is caused by chronic exposure to high BP. As population ages, both HT and Hypertensive Heart Disease prevalence increase. Genetic and hemodynamic factors interact to cause Hypertensive Heart Disease in patients with hypertension. In patients with Hypertensive Heart Disease , abnormalities of both myocardial relaxation and passive filling may be detected sometimes on echocardiography (echo). These diastolic dysfunctions are due to various mechanisms but central to the pathophysiology is an increase in myocardial stiffness. Early symptoms of myocardial stiffness caused by left ventricular hypertrophy (LVH) is a good early indicator for cardiovascular target organ damage in patients with HT and Hypertensive Heart Disease . Hypertensive Heart Disease patients constitute a group in which intensive BP treatment with drugs to strict targets are shown to yield favourable benefit risk ratios. As such, the identification of Hypertensive Heart Disease patients becomes paramount.

An electrocardiogram (ECG) monitors and records the heart's electrical activity. ECG is insensitive to detect diastolic dysfunction with sensitivity from 12% to 50%. An echo takes a picture of the heart using ultrasound. Echo can be used to diagnose diastolic function, however, no one single echo parameter can make the diagnosis. Multiple echo parameters have been proposed including mitral inflow velocity pattern, pulmonary vein flow patterns and tissue Doppler measurements, but imprecise. Existing ultrasound scans cost in the range of US$300-$600 which are reimbursable under Medicaid (the payer). A coronary angiography examines the flow of blood through the heart by inserting a catheter into the heart. It is too invasive and too costly. Therefore, there is appealing need to have a cheaper non-invasive solution that would be able to detect diastolic function. That will have largest impact on patients management and on payers.

A cheap, non-invasive and sensitive solution that permits detection via auscultation of abnormal heart sounds, indicating stiff heart muscle associated with Hypertensive Heart Disease among HT patients is critically needed. Cardiac auscultation (listening to heart sounds) is possible option as heart sounds are associated with myocardial function and dysfunction .In a normal heart, two heart sounds (S1 and S2) are audible, corresponding to closure of the mitral and aortic heart valves respectively. A third heart sound S3, occurring after S2 is present in some heart failure. A fourth heart sound S4, occurring just before S1, is due to forceful contraction of the atrium to overcome a stiff or hypertrophic left ventricle . Human ears are not well equipped to detect such abnormities consistently with a conventional stethoscope. Therefore, investigators propose to develop a low power, non-invasive, portable device which is based on Wireless Sensor Node (WSN) technology to achieve our goal of portable auscultation.Proposed device will allow a monitoring/recording of heart sounds in-situ and perform preliminary assessment of diastolic function that is physiologically meaningful, reproducible and validated. Multiple devices can also be placed and used concurrently at different sites over the torso to enhance chances of detecting abnormal heart sounds.