Mitral regurgitation and characteristic changes in impedance cardiogram

Cardiovascular Diseases Diagnosis by Impedance Cardiography

Cardiovascular disease (CVD) represents the leading cause of mortality worldwide. In order to diagnose CVDs, there are a range of detection methods, among them, the impedance cardiography technique (ICG). It is a non-invasive and low-cost method. In this paper, we highlight recent advances and developments of the CDVs diagnosis mainly by the ICG method. We considered papers published during the last five years (from 2017 until 2022). Based on this study, we expressed the need for an ICG database for the different CDVs.

Ambulatory impedance cardiography in hypertension: a validation study

The management of hypertension is improved by knowledge of the hemodynamics underlying blood pressure. Impedance Cardiography (ICG) provides data on a range of hemodynamic variables that affect blood pressure. However, ICG captures only fixed descriptions of hemodynamic characteristics. Improvements in ambulatory technology have led to the development of the Ambulatory Impedance Monitor (AIM) which records hemodynamic data during the activities of daily living. The purpose of this study was to evaluate the sensitivity of the AIM to detect hemodynamic changes associated with postural shift in persons with hypertension. Using a repeated measures cross-over design, sitting and standing hemodynamic measures were taken in seventeen persons with hypertension while wearing the AIM-BpTRU system designed for standard office use and the AIM-Spacelabs system designed for ambulatory monitoring. Both AIM-blood pressure monitoring systems detected significant changes from sitting to standing posture in heart rate (p=0.03), stroke volume (p=0.002), left ventricular ejection time (p<0.001), systemic vascular resistance (p=0.03) and diastolic blood pressure (p<0.001). Additionally, both systems generated measures of cardiac function that were positively correlated (p<0.001) and not significantly different (p>0.05). Our findings support previous work and demonstrate that the AIM provides valid and reliable estimates of cardiac function in persons with hypertension.

Analysis of the O-wave in acute right ventricular apex impedance measurements with a standard pacing lead in animals

Modern pacemakers (implantable devices used for maintaining an appropriate heart rate in patients) can use an intracardiac ventricular impedance signal for physiological cardiac stimulation control. Intracardiac ventricular impedance from nine animal subjects is analysed and presented (seven sheep: 49.0 +/- 6.5 kg, sinus rhythm 100.3 +/- 16.5 beats min(-1), average impedance 629.8 +/- 72.6 ohms; and two dogs: 30 kg each, sinus rhythm 86.0 beats min(-1), 862.1 ohms and 134.0 beats min(-1), 1114.6 ohms, respectively). The averaged curve and standard deviation curve of the impedance in sinus rhythm were analysed in MATLAB to clarify and study consistent impedance shape over one heart cycle. In eight of nine (89%) animal subjects, a consistent impedance slope change (notch) was observed in the early stage of the cardiac filling phase. This result was reproduced in an additional subject with simultaneous echocardiographical measurements of mitral valve blood flow. The notch occured soon after rapid early filling (E-wave in mitral flow) but prior to ventricular filling caused by atrial contraction, indicating that the impedance notch was caused by rapid ventricular filling and that it might be a sensed feature of diagnostic value. The intracardiac impedance notch in the present study had similar features to the non-invasive transthoracic impedance O-wave reported by others, and it is shown here that an O-wave is found in intracardiac impedance signals, strongly suggesting that the non-invasive O-wave is caused by cardiac events.

A practical, cost-effective, noninvasive system for cardiac output and hemodynamic analysis

Impedance cardiography is a relatively inexpensive, noninvasive technique for measuring cardiac output on the basis of resistive changes in the thorax to electrical current flow. In conjunction with blood pressure monitoring and physiologic maneuvers, the technique may be used to monitor thoracic and total body fluid volume and express a variety of contractility indexes as well as relative and absolute measurements of stroke volume. We have tested hemodynamics in our laboratory by using a cost-effective, powerful microcomputer-based portable noninvasive technique, which makes possible the ensemble averaging of impedance cardiographic waveforms. In conjunction with physiologic maneuvers, the technique has been implemented at our institution and has provided helpful information in our experience in evaluating volume overload, hypertension, hypotension, shock, and heart failure. It is hoped that this noninvasive, relatively cost-effective approach will be more widely appreciated in the future, given the economic realities of medicine today.