James N. Karnegis

Physiological correlates of the cardiac thoracic impedance waveform

Abstract A high frequency, constant sinusoidal current can be passed through the chest by a noninvasive technique and pulsatile changes in the thoracic impedance recorded. These pulsations are related to the beating of the heart. Three major components are present. One component shows an increase in impedance, is associated with atrial contraction, and consistently follows the P wave of the electrocardiogram. The other two waves show a decrease in impedance. The first is associated with ventricular systole, and corresponds in time with the QRS complex of the ECG. The systolic wave is then followed by the third component, which also shows a decrease in impedance, but occurs in diastole. In instances of arrhythmias the deflection associated with the P wave occurs independently of the other two deflections. The impedance change waveform is similar to the pattern of blood flow in the venae cavae and the pulmonary veins. It is possible that the impedance changes are related to the flow of blood in these venous circuits, and the heart.

Persistent left superior vena cava, fibrous remnant of the right superior vena cava and ventricular septal defect☆

Abstract We have reported a case of persistent left superior vena cava associated with a nonfunctional right superior vena cava. Twenty-nine cases of this venous pattern with anatomic study were found in the literature. Among these, as in the case here reported, only 3 showed an anatomic vestige, in the form of an atretic cord, of the right superior vena cava. In our case a ventricular septal defect was also present, which yielded certain features like those in origin of both great vessels from the right ventricle. The venous anomalies yielded an unusual course of the catheter during cardiac catheterization. These anomalies were identified by venous angiocardiography.

Comparison of exercise-positive with recovery-positive treadmill graded exercise tests☆

A treadmill exercise test response may become positive because a diagnostic electrocardiographic ST-segment shift occurred during exercise, or, less often, because it occurred only during the recovery period after exercise had been completed. Factors that may be related to these 2 different responses in subjects enrolled in the Program of Surgical Control of Hyperlipidemia were investigated. No differences were found with regard to age, sex, level or location of Minnesota electrocardiographic Q-QS codes, number of narrowed coronary arteries, presence of collateral coronary artery circulation, ejection fraction, number of abnormally moving left ventricular wall segments, heart rate, systolic and diastolic blood pressure, double product, total exercise time, exercise-induced angina, or maximally achieved exercise heart rate or double product. Thus, the same significance should be attributed to a recovery-positive as to an exercise-positive treadmill test, and electrocardiographic, hemodynamic and angiocardiographic variables do not distinguish between subjects who exhibit these 2 different responses.

Development and evolution of electrocardiographic Minnesota Q-QS codes in patients with acute myocardial infarction

The development of ECG Minnesota Q-QS codes and their subsequent evolution were studied in the first 692 subjects to enter the POSCH program who had had one MI. The mean interval from MI to entry into the study was 2.2 years. Sixty-three percent of the subjects developed the most significant code with the infarction. By the time the subjects entered the study, the codes had commonly regressed to a lower level, disappearing altogether in 34%. The likelihood of complete regression varied inversely with the significance of the code. There was no significant difference between the groups with disappearance and with retention of a Q-QS code as to time since MI, the extent of coronary arterial disease, or the age or sex of the subject. In about half of the subjects the original code did not change with time and in 21% to 44% the code increased to one of a higher level of significance.

The risk of diagnostic cardiovascular catheterization.

This report details a prospective study of the risk of diagnostic cardiac catheterization performed in a private, community hospital. Over the first 131 months of operation of our laboratory, 745 adult patients underwent diagnostic cardiac catheterization consisting of 2,676 various catheterization procedures. Six patients experienced seven major complications; two of these complications left a permanent deficit. There were no deaths during catheterization and none later which were attributable to it. The risk to the patient of having a major complication associated with a cardiac catheterization in our series was 0.8 per cent. The risk to the patient of having a major complication when a catheterization procedure was performed was 0.3 per cent. The risk of having a complication resulting in a permanent sequela was 0.07 per cent. We conclude that diagnostic cardiac catheterization can be accomplished with little risk to the patient, either of death or of other major complication.

The phonocardiogram in idiopathic dilatation of the pulmonary artery

Abstract Eight patients with idiopathic dilatation of the pulmonary artery were studied by right heart catheterization and phonocardiography. The data suggest that, although there is no single diagnostic feature, a rather characteristic pattern is found on analysis of the phonocardiogram; it consists of a normal first heart sound, a systolic click, a faint or absent pulmonic systolic murmur, wide splitting of the second heart sound which is usually fixed, and occasionally a diastolic murmur at the pulmonary area. This distinctive pattern may prove to be of value in the diagnosis of idiopathic dilatation of the pulmonary artery.

Relation between Q-QS changes on the rest electrocardiogram and left ventricular function with healed myocardial infarction

In the Program of Surgical Control of Hyperlipidemia, the relation of the Minnesota Q-QS codes for rest electrocardiograms to left ventricular (LV) function was studied in patients with healed myocardial infarction (MI). Of 838 subjects enrolled in the study, 477 (57%) had codable Q-QS patterns at the time of randomization. There was an extremely high correlation between the level of the Minnesota code and concurrent LV function, the latter being determined on left ventriculography by both ejection fraction and the number of segmental wall motion abnormalities. Subjects without a Q-QS code had less myocardial damage than did those with a code present in a single cardiac area. Extent of LV damage correlated with the level of significance of the Q-QS code, and when the code was present in only 1 cardiac location damage was greatest if the anteroseptal area was involved. Q-QS codes present in 2 rather than 1 cardiac area were associated with an even greater degree of LV damage. A previous study has shown a strong correlation between LV function and the Minnesota codes when the latter were recorded 0.5 to 5 years (mean 2.2) earlier at the time of the acute MI. The present data show that the relation between LV function and the Minnesota codes after an acute MI persists over time and is even stronger when both are determined in the healed state at a time remote from the acute event.

Directional ST-segment deviation in graded exercise tests correlated with motion of the individual segments of the left ventricular wall

An exercise test may be characterized as positive because of the production of either electrocardiographic ST-segment depression or elevation. The relationship of exercise-induced ST-segment deviation to the specific motion abnormalities of the individual segments of the left ventricular wall was investigated. The first 280 subjects to enter the Program of Surgical Control of Hyperlipidemia were studied by treadmill exercise testing and left ventriculography. The results showed that exercise-induced ST-segment elevation could occur without evidence in the resting subject of either dyskinesia or aneurysm of the left ventricle, that the area of left ventricular damage was much greater in subjects with exercise-induced ST-segment elevation than in those with ST-segment depression, and that wall motion abnormalities were concentrated in the inferoposterior area in the group with ST-segment elevation, but were generally scattered throughout the left ventricular wall in the group with ST-segment depression.

The Q—1 interval of the phonocardiogram: In patients with ventricular septal defect, patent ductus arteriosus and Blalock anastomosis

Abstract Eighteen patients with varying degrees of left-to-right shunt at the ventricular and pulmonary artery level (in which the shunt flow passes through the mitral valve) were studied by right heart catheterization and phonocardiography. There was good correlation between the relative size of the left-to-right shunt and the duration of the phonocardiographic Q-1 interval. Possible explanations of this finding are discussed. The measurement of the Q-1 interval in these patients may be of clinical value in evaluating the relative size of the left-to-right shunt and in assessing postoperative results.

The effect of atrial rhythm on the thoracic impedance cardiogram.

We have observed that the thoracic impedance waveform is altered when there is a change in atrial rhythm. In order to investigate this, we selected for review impedance cardiograms of patients with various atrial rhythms. The study showed that the thoracic impedance waveform displays characteristic deflections that are specifically associated with different atrial rhythms and are analogous to those seen on the electrocardiogram. The finding that the waveform was sensitive even to the small atrial movements discernible during the rhythm of coarse atrial fibrillation was consistent with the possibility that blood flow within the vena cave-right atrial and/or the pulmonary venous-left atrial systems may be important in the genesis of the cardiac thoracic impedance waveform.