Acute pericardial distension in pigs: effect of fluid conductance on body surface electrocardiogram QRS size.

OBJECTIVES: Pericardial effusion has long been associated with low voltage of the surface electrocardiogram and its clinical utility is well known. The cause of this reduced QRS voltage has usually been attributed to short circuiting of the impulses by the pericardial fluid, but its precise mechanism has not been clearly elucidated. Therefore, we investigated this phenomenon by instilling various fluids with different resistances in increasing volumes into the pericardial space to finally produce acute cardiac tamponade. METHODS: Acute cardiac tamponade was produced 65 times in 25 closed chest pigs with a mean weight of 57(SEM 1.2) kg. A sufficient quantity (mean = 200 ml) of plasma, saline, blood, and blood with varying packed cell volume was introduced into the pericardial space in 60 ml increments to decrease systemic and pulmonary pressures to 50% of control to produce cardiac tamponade. At that point intrapericardial pressure had increased to 15-20 mm Hg. Resistivity values for the instilled fluids are 150 omega-cm for blood, 60 omega-cm for plasma, and 50 omega-cm for saline. RESULTS: Mean limb and precordial lead QRS voltage fell significantly, with no significant differences among these fluids. Electrocardiograph recordings from a unipolar electrode catheter in the right ventricle showed an increase in R wave voltage, but body surface recordings of stimuli introduced into the right atrium via a bipolar electrode catheter showed no amplitude change. CONCLUSIONS: In considering possibilities such as internal shunting of cardiac currents by intrapericardial fluid, distance of the heart from body surface electrodes, and change in cardiac position, the results are best explained by a reduction of cardiac volume and size during cardiac tamponade. This conclusion confirms Brody's hypothesis.

Varied manifestations of left atrial myxoma and the relationship of echocardiographic patterns of tumor size.

Four cases of left atrial myxoma with varied clinical manifestations were diagnosed with echocardiographic studies prior to cardiac catheterization and surgery. The unusual clinical features include Raynaud's phenomenon and intermittent claudication. The echocardiographic features of the atrial myxoma appear to be related to tumor size. Systematic echocardiographic evaluation of patients with mitral valvular disease and systemic and cerebral vascular insufficiency will undoubtedly increase the positive diagnostic results in patients with atrial myxomas. Removal of these tumors results in normalization of the echocardiographic pattern.

Prognostic significance of the development of left bundle conduction defects following aortic valve replacement.

The association of intraventricular conduction defects and aortic valvular disease is widely recognized. This study was undertaken to evaluate the effects on survival of left bundle conduction defects (LBCDs) as a consequence of aortic valve replacement. A total of 133 patients were followed between 1 and 70 months after operation, with a mean follow-up of 32.1 months. The incidence of intraoperative LBCDs was 31.6% or 42 patients. There were 13 deaths in the group of 42 patients with LBCDs compared to eight deaths in the group of 91 patients without such abnormalities (p less than 0.01). Sudden death occurred in five of 42 patients with postoperative LBCDs and two of 91 patients with normal intraventricular conduction (p less than 0.025). The survival rate in these patients with significant aortic stenosis and normal intraventricular conduction was 89.9%, whereas if LBCD had occurred after operation, the survival rate was 65.7% (p less than 0.005). If the LBCD was accompanied by a left axis deviation, the survival rate was 21.7%. Sudden death may be due either to a tachyarrhythmia or perhaps to progression from LBCD to complete heart block or trifascicular block. It is important that this group of patients be monitored closely after operation. There may be an indication to insert prophylactic permanent pacemakers in this group.

Intravenous digital subtraction angiography with iohexol.

Iohexol is a nonionic water-soluble iodinated contrast medium with chemical and physical properties similar to those of metrizamide. A randomized double-blind study was performed in 40 patients undergoing intravenous digital subtraction angiography for suspected carotid and vertebral disease to compare the radiographic imaging quality and side effects of iohexol with those of Renografin-76 (diatrizoate meglumine and diatrizoate sodium). The use of iohexol yielded a higher percentage of "excellent" images with a lesser incidence of image degradation due to swallowing and motion. Iohexol was also associated with milder and less frequent patient discomfort. No clinically significant changes in laboratory data parameters were observed with either contrast medium.

Carotid sinus syndrome. Report of five cases and review of the literature.

Five cases of carotid sinus syndrome are presented. The syndrome is defined by spontaneous attacks of dizziness and fainting which can be reproduced by graded pressure on one carotid sinus. Three forms of the clinical syndrome, cardioinhibitory, vasodepressor, and cerebral, are discussed. The hyperactive carotid sinsu reflex, in which there is ventricular asystole lasting at least 3 seconds or a decrease of more than 50 mm Hg in systolic and diastolic blood pressure, should be differentiated from this syndrome. Treatment modalities include reassurance, drugs, radiotherapy, cardiac pacemakers, and surgical approaches. Carotid sinus syndrome should be considered in the differential diagnosis of unexplained syncope, arteriovenous block, or inappropriate sinus bradycardia.

Vectorcardiographic manifestations of experimental right ventricular necrosis.

This study was carried out to evaluate the possible usefulness of the VCG in the diagnosis of right ventricular necrosis. Myocardial necrosis was produced by injecting 40% formalin into the ventricular walls of 21 open-chest mongrel dogs. The injections were made in the inferior wall of the left ventricle in eight dogs (Group A) and in the inferior wall of the right ventricle in 13 dogs (Group B). Analysis of vectorcardiographic QRS loops obtained before and two hours after the injections revealed that both left and right ventricular necrosis resulted in a decrease in: maximum inferior amplitude, inferior amplitude at 10 and 20 msec. and maximum frontal plane angle. In Group A, six dogs had counterclockwise initial forces in the frontal plane before the injections and these became clockwise following the injections. In Group B, nine dogs had counterclockwise initial forces in the frontal plane before the injections and these remained counterclockwise following the injections. The only consistent QRS change in scalar ECGs that occurred after the injections was the development of small Q waves in the six dogs in Group A that manifested clockwise initial forces in the frontal plane. The VCG performed in serial fashion may be more sensitive than the 12 lead ECG for detecting right ventricular inferior wall necrosis in the experimental animal. Application of these findings to the diagnosis of myocardial infarction in humans requires further investigation.

Improved electrocardiographic criteria for the diagnosis of inferior myocardial infarction.

New electrocardiographic (ECG) criteria for the diagnosis of inferior myocardial infarction (IMI) are proposed. The criteria are based upon the relationships between portions of the vectorcardiographic (VCG) QRS loop in the frontal plane and the corresponding portions of the ECG QRS complexes recorded in leads II and III. The application of the proposed criteria requires that the tracings be obtained with three-channel ECG machines so that the temporal relationships between the QRS complexes in lead II and those in simultaneously recorded lead III can be inspected. This type of analysis of the ECG permits important features of the contour of the VCG QRS loop to be predicted. The proposed ECG criteria for the diagnosis of IMI are: in the absence of counterclockwise rotation in the frontal plane, (1) Q waves of 30 msec or longer in lead II or (2) regression of initial inferior forces from lead III to lead II. The proposed ECG criteria were evaluated in an initial series of 333 patients and, using a blind experimental design, in a confirmatory series of 94 patients. The performance of the proposed criteria was statistically superior to that of two sets of ECG Q-wave criteria and comparable to that of the VCG criteria of Starr et al.

Follow-up catheterization of patients with myocardial infarction during coronary artery bypass surgery.

Of 197 consecutive patients having aortocoronary bypass grafts over a 30 month period, 38 (19 per cent) had ECG evidence of myocardial infarction. The infarctions occurred more commonly in patients receiving multiple grafts. The infarctions were usually in areas supplied by grafted vessels. The infarctions occurred most often in the inferior wall, even when multiple vessels were grafted. Eleven patients with intraoperative infarction have had repeat postoperative coronary arteriograms. Seven had all grafts patent; three of these patients had hypokinesis of the infarcted wall. Four of the 11 patients had one or more occluded grafts; three of these patients had an area of hypokinesis. We conclude that intraoperative myocardial infarction is a common problem in aortocoronary bypass surgery and is not necessarily caused by graft occlusion.

Prophylactic digitalization for coronary artery bypass surgery.

One hundred and twenty patients undergoing aortocoronary bypass procedures were randomly placed into control and digitalized groups. All were initially in normal sinus rhythm and without evidence of congestive heart failure. Supraventricular arrhythmias occurred in 17 of 66 controls and in only three of 54 digitalized patients (P less than 0.01). There was no evidence of digitals toxicity. Based on this evidence we recommend prophylactic digitalization for patients having aortocoronary bypass operations.