Recorded heart sounds for identification of ventricular tachycardia

Protocol of the Swiss Longitudinal Cohort Study (SWICOS) in rural Switzerland

INTRODUCTION

Increased longevity and consequent major changes in demographics and population lifestyles necessitate new approaches to reduce the burden of ageing-related diseases (including cardiovascular disease) and maintain an optimal quality of life. This study aims to examine and longitudinally follow health status and disease risk factors in a Swiss rural cohort, evaluating all health-related research and practice disciplines to assure development of new implementable and successful preventive strategies for healthy ageing.

METHODS AND OBJECTIVES

Small Swiss villages with low migration rates will be selected for this study. 2 villages (Cama/Lostallo) have already been selected as initial study sites. All residents (age ≥6 years, no upper age limit) are eligible. The target enrolment number per village is 300. Examinations and measurements encompass medical history, anthropometry, cardiac and vascular health, pulmonary function, physical performance, nutritional, mental and emotional status, biochemical and molecular analyses. Follow-up examinations (identical to baseline) will be performed after 5 and 10 years, and in 10-year intervals thereafter. The major objective is to assess, and observe change in, health status over time in a prospective manner. Secondary objectives are to: (1) identify 'hidden' (asymptomatic and/or unrecognised) health problems which enhance risk for chronic diseases; (2) identify barriers to accessing healthcare and adapting health behaviours; (3) evaluate efficacy of present preventive strategies and recommendations; (4) evaluate knowledge and attitude towards ongoing health programmes and public health recommendations; (5) monitor change and progress towards the national health objectives; (6) formulate new preventive strategies and recommendations based on the findings and knowledge base of the past 10 years; (7) formulate models for successful prevention of chronic diseases and for healthy ageing.

ETHICS AND DISSEMINATION

The Ethics Committee of Nordwest-und Zentralschweiz approved this study (EKNZ 2014-209). It is registered at ClinicalTrials.gov (NCT02282748). Findings will be disseminated through scientific articles/presentations and public events.

Effects of weight on blood pressure at rest and during exercise

Body weight (BW) and blood pressure (BP) have a close relationship, which has been accounted for by hormonal changes. No previous study has evaluated the effect of wearing an external weight vest on BP to determine whether there is a simple mechanism between BW and BP. Seventeen healthy volunteers underwent weight reduction (WR) through caloric restriction. Before and after WR, BW, body fat percentage and BP at rest and during exercise were measured. Before and after WR, exercise testing was performed twice with the random allocation of a weight vest (10 kg) during one of the tests. Linear regression was used to detect independent associations between BP and the weight vest, BW and body fat percentage. BW decreased from 89.4 ± 15.4 kg to 79.1 ± 14.0 kg following WR (P<0.001). WR led to significant decreases in BP at rest (from 130.0/85.9 mm Hg to 112.5/77.8 mm Hg, P<0.001 for systolic and diastolic BPs) and during exercise. The weight vest significantly increased BP at rest (to 136.1/90.7 mm Hg before and 125.8/84.6 mm Hg after WR) and during exercise. Linear regression analysis identified an independent association between the weight vest and BP (P=0.006 for systolic BP and P=0.009 for diastolic BP at rest). This study demonstrates that wearing an external weight vest has immediate effects on BP at rest and during exercise independent of BW or body fat. More research is needed to understand the physiological mechanisms between weight and BP.

Heart sounds analysis via esophageal stethoscope system in beagles

Esophageal stethoscope is less invasive and easy to handling. And it gives a lot of information. The purpose of this study is to investigate the correlation of blood pressure and heart sound as measured by esophageal stethoscope. Four male beagles weighing 10 to 12 kg were selected as experimental subjects. After general anesthesia, the esophageal stethoscope was inserted. After connecting the microphone, the heart sounds were visualized and recorded through a self-developed equipment and program. The amplitudes of S1 and S2 were monitored real-time to examine changes as the blood pressure increased and decreased. The relationship between the ratios of S1 to S2 (S1/S2) and changes in blood pressure due to ephedrine was evaluated. The same experiment was performed with different concentration of isoflurane. From S1 and S2 in the inotropics experiment, a high correlation appeared with change in blood pressure in S1. The relationship between S1/S2 and change in blood pressure showed a positive correlation in each experimental subject. In the volatile anesthetics experiment, the heart sounds decreased as MAC increased. Heart sounds were analyzed successfully with the esophageal stethoscope through the self-developed program and equipment. A proportional change in heart sounds was confirmed when blood pressure was changed using inotropics or volatile anesthetics. The esophageal stethoscope can achieve the closest proximity to the heart to hear sounds in a non-invasive manner.

Identification of hemodynamically unstable arrhythmias using subcutaneous photoplethysmography

INTRODUCTION

Determination of hemodynamic status is central to arrhythmia management in the inpatient setting. In contrast, therapy decisions in implantable cardioverter defibrillators (ICDs) are based exclusively on the arrhythmia's electrical signature. Hemodynamic sensing in ICDs would allow tailoring of therapy according to perfusion status. Subcutaneous photoplethysmography (PPG) is an attractive technology for this application because it responds to changes in arterial pressure and can be readily incorporated into the housing of implanted devices. This study evaluated the accuracy of PPG in identifying hemodynamically unstable simulated arrhythmias in an animal model.

METHODS AND RESULTS

Rapid atrial and ventricular pacing was used to simulate arrhythmias in an acute preparation of 7 healthy dogs. Aortic pressure and subcutaneous PPG were simultaneously recorded. Simulated arrhythmias were defined as hemodynamically unstable if aortic pressure decreased by >or=15 mmHg, marginally unstable if pressure decreased by 5-15 mmHg, and hemodynamically stable if pressure either increased or decreased by no more than 5 mmHg. An average of 56 arrhythmias were simulated in each animal. Changes in pressure and PPG output were highly correlated, with correlation coefficient of 0.7-0.9. Subcutaneous PPG identified hemodynamically unstable episodes with a sensitivity of 100% for 6 subjects and 80% for 1 subject. Specificity was more than 90% for 6 subjects and was 50% for 1 subject.

CONCLUSIONS

Subcutaneous PPG detects hemodynamically unstable simulated arrhythmias in an acute canine preparation. If successfully validated in humans, this technology may allow ICD therapy to be specifically tailored according to the hemodynamic status of the arrhythmia.