American heart journal
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American heart journal · Jun 1995
Comparative StudyHemodynamic importance of preserving the normal sequence of ventricular activation in permanent cardiac pacing.
Pacing the right ventricle in the apex profoundly modifies the sequence of activation and thus the sequence of contraction and relaxation of the left ventricle. To evaluate the relative importance of preserving normal ventricular activation sequence and optimal atrioventricular (AV) synchrony in permanent pacing, we compared the effects of three pacing modes: AAI, preserving both normal AV synchrony and normal activation sequence; DDD, with complete ventricular capture that preserves only AV synchrony; and VVI, disrupting both, at rest and during exercise. Hemodynamic and radionuclide studies were performed in 11 patients who had normal intrinsic conduction and who were implanted on a long-term basis with a DDDR pacemaker for isolated sinus node dysfunction. ⋯ This improvement in LV systolic function resulted principally from the increase in septal ejection fraction. LV filling also was improved in AAI as demonstrated by a significant increase in peak filling rate at rest and during exercise. These data show the importance of preserving, whenever possible, not only normal AV synchrony but also normal ventricular activation sequence in permanent cardiac pacing.
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American heart journal · May 1995
Comparative StudyAtrial wall tension changes and the release of atrial natriuretic factor on relief of cardiac tamponade.
Cardiac tamponade causes elevation and equalization of cardiac filling pressures, sodium and water retention, and a paradoxically low plasma atrial natriuretic factor (ANF) concentration despite increased intraatrial pressures. Recent reports suggested that plasma ANF concentrations rise after relief of tamponade. The purposes of the present study were (1) to determine the time course and extent of ANF release on relief of cardiac tamponade; (2) to measure the atrial transmural wall pressures, atrial sizes, and atrial wall tension changes associated with relief of tamponade; and (3) to determine the biologic activity of elevated plasma ANF during and after relief of tamponade. ⋯ The rise in ANF was negatively correlated with atrial pressures but positively correlated with atrial transmural pressures, atrial size, and calculated wall tension. Plasma ANF levels peaked at 515 +/- 95 pg/ml 40 minutes after relief of tamponade and leveled off at 140% to 180% of the pretap concentrations. Plasma cGMP exhibited a slightly delayed but similar time course to the rise in ANF levels, and urine flow rate increased fourfold in the 8 hours after relief of tamponade.(ABSTRACT TRUNCATED AT 250 WORDS)
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American heart journal · May 1995
Comparative StudyUse of P-wave-triggered, P-wave signal-averaged electrocardiogram to predict atrial fibrillation after coronary artery bypass surgery.
Atrial fibrillation occurs commonly after coronary artery bypass surgery. However, despite numerous attempts at prediction, no accurate and generally accepted method exists to predict its occurrence. P-wave-triggered P-wave signal averaging was performed on 54 patients before coronary artery bypass surgery to evaluate the utility of this method to predict atrial fibrillation after coronary artery bypass surgery. ⋯ Other clinical variables such as P-wave duration in ECG lead II, left ventricular hypertrophy on ECG, age, sex, hypertension, and left ventricular ejection fraction were not significantly different between the two groups. With a cut point of 155 msec, chi-squared analysis revealed a p value of < 0.005, yielding a sensitivity of 69%, a specificity of 79%, a positive predictive value of 65%, and a negative predictive value of 82%. Signal-averaging of the P wave in patients before coronary artery bypass surgery provides a good predictor of postoperative atrial fibrillation.
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American heart journal · May 1995
Comparative StudyEcho Doppler evaluation of patients with acute mitral regurgitation: superiority of transesophageal echocardiography with color flow imaging.
Acute mitral regurgitation is a medical emergency that requires prompt, accurate diagnosis and urgent therapy. Although the use of echo Doppler imaging has been described in these patients, preliminary observations have suggested that color flow Doppler performed from the standard transthoracic windows may underestimate the severity of mitral insufficiency in this setting. The aim of this study was to compare transesophageal color Doppler quantitation of regurgitation with results obtained from standard transthoracic windows in patients with acute, severe mitral regurgitation. ⋯ At first examination patients were critically ill, with elevated pulmonary wedge pressures (mean 27 +/- 7 mm Hg) and V waves (mean 45 +/- 10 mm Hg). Fifteen of the patients underwent emergency surgery, and the overall hospital mortality rate was 12%. Maximal color flow jet areas were significantly greater on transesophageal scanning (mean 10.5 cm2) compared with transthoracic color jets (mean 2.3 cm2).(ABSTRACT TRUNCATED AT 250 WORDS)