Limitations of the cardiokymograph for assessing left ventricular wall motion

Evaluation of signal-averaged cardiokymography for the detection of ischaemic left ventricular dysfunction

Cardiokymography (CKG) is a non-invasive method for the detection of patients with coronary artery disease (CAD). Issues of the present study were to evaluate the feasibility, sensitivity and specificity of a recently developed signal-averaged CKG system for detecting patients with pharmacologically induced ischaemic left ventricular wall motion abnormalities (WMA) during pharmacologic stress echocardiography (SE). Precordial CKG curves were recorded in 100 consecutive patients who underwent dobutamine-SE for suspected CAD. For interpretation, CKG curves were classified into three different types, depending on the degree of systolic outward motion. CKG test results were regarded as positive (indicating myocardial ischaemia) if there was a change of the baseline CKG type at peak pharmacologic stress. The CKG test results were positive in 18 of 27 patients with a pathologic dobutamine-SE (sensitivity 67%), but did not show any change of the prior CKG type in 57 of 69 patients with a normal SE (specificity 83%). Patients with a true positive CKG test had significantly (P<0.05) more echocardiographic segments with WMA than patients with a false negative CKG test.

CONCLUSIONS

Signal-averaged CKG can detect patients with ischaemic ventricular dysfunction. Sensitivity of CKG in detecting patients with WMA depends on the extent of left ventricular ischaemia. Further studies are needed to define the diagnostic value of signal-averaged CKG in the non-invasive detection of patients with suspected CAD.

Thoracocardiography. Part 1: Noninvasive measurement of changes in stroke volume comparisons to thermodilution

The thoracocardiograph (TCG) is a new noninvasive monitoring device that measures cardiac oscillations transmitted to the external surface of the thorax. It consists of 2.5 cm in height, elastic inductive plethysmographic transducers placed transversely in the proximity of the xiphoid process to provide changes in cross-sectional area on a transverse plane across the minor ventricular axis. Cardiac oscillations synchronous with each heart beat are extracted from the respiratory signal during breathing with an ensemble-averaging technique using the electrocardiograph as a trigger pulse. The average cardiac waveform at locations near the xiphoid process in normal humans has the appearance of a ventricular volume curve. The latter is also found in the majority of patients with heart disease although in some, outward (dyskinetic) rather than inward motion during systole occurs at one or more locations of the TCG transducers. As in echocardiography, such findings are consistent with ischemic or scarred myocardium invalidating computation of changes in stroke volume from such sites. In anesthetized dogs and critically ill patients with normal ventricular wall motion, changes in TCG derived ventricular volume waveform amplitudes agreed well with changes of thermodilution estimates of stroke volume during atrial pacing and fluid loading in the dogs on the one hand and with application of extrinsic positive end-expiratory pressure (PEEP) in patients on the other hand. Thoracocardiography has the potential for noninvasive, continuous monitoring of stroke volume and cardiac output as well as for detection of ischemic or scarred myocardium.

The resting cardiokymogram: distribution of morphologies in normal patients and in patients with coronary heart disease

The cardiokymograph, a relatively new noninvasive device capable of recording anterior left ventricular segmental wall motion, was used to evaluate the frequency and type of wall motion abnormalities in 25 normal patients and in 109 patients with ischemic heart disease. Of the 25 patients with normal coronary arteries and normal left ventriculograms, 24 had smooth systolic inward motion which morphologically resembles the normal pattern of systolic shortening as measured in experimental animals by various length gauges. In patients with angiographically established coronary artery disease but normal left ventriculograms and no previous myocardial infarction (MI), systolic outward motion was significantly more common than in normal patients. The most common systolic outward motion pattern seen in this group was partial outward motion characteristic of early stages of myocardial ischemia in experimental animals. In contrast, holosystolic outward motion, characteristic of severe ischemia in animals, was seen most commonly in patients with MI (73% anterior vs. 28% inferior). Thus, holosystolic outward motion was characteristic of MI especially when acute and involving the anterior wall, while partial systolic outward motion was the more common pattern in ischemic heart disease without MI, and systolic inward motion was the pattern most commonly seen in normals.