A model to predict survival at time of postcardiotomy intraaortic balloon pump insertion.

To facilitate timely application of new forms of cardiac support to patients at highest risk after cardiotomy despite conventional support with the intraaortic balloon pump, an accurate prediction of survival must be available at the time of weaning from cardiopulmonary bypass. We, therefore, acquired 240 demographic, disease, and perioperative characteristics of 322 patients (mortality rate, 48.4%) who required IABP support to separate from bypass. Four variables available before or within 10 minutes of the first attempt at weaning from bypass significantly predicted mortality by stepwise logistic regression: complete heart block as demonstrated by need for temporary pacing at weaning (p < 0.001), advanced age (p < 0.002), preoperative blood urea nitrogen concentration (p = 0.036), and female sex (p = 0.048). An equation generated by the logistic model predicted a 72.2% survival rate in the 25% of patients at least risk (actual survival rate, 71.6%); in the 25% at greatest risk, death was predicted in 73.0%, and the actual mortality rate was 74.1%. The equation was then prospectively applied to 330 intraaortic balloon pump-supported patients managed at another institution. The overall mortality rate there was 41.2%; in the 25% at least risk, predicted survival rate was 70.5% (actual survival rate, 77.1%), and in the 25% at greatest risk, predicted mortality rate was 75.7% (actual mortality rate, 62.7%). Thus, retrospectively at one institution and prospectively at another, the equation generated by this model based only on data available at the time of weaning from bypass was able to define one subgroup of patients 2.6 to 2.7 times as likely to die as another subgroup from within similar cohorts.(ABSTRACT TRUNCATED AT 250 WORDS)

Documentation of experimentally induced thrombus formation using intravascular ultrasound.

The purpose of the present study is to assess the ability of intravascular ultrasound to detect acute dynamic thrombus formation in canine blood vessels with damaged endothelium. Ultrasound catheters (20 MHz) were placed in the femoral arteries of anesthetized dogs, and imaging transducers were positioned at the sites of external constrictors applied to areas of endothelial injury. Flows were measured with externally applied Doppler crystals placed proximal to the constrictors. Twenty experimental procedures were performed in 18 dogs. Four procedures were performed using the InterTherapy system (4.9 Fr catheters) and 16 procedures were performed using the Boston Scientific/Diasonics system (6.0 and 4.8 Fr catheters). After injuring the endothelium by rubbing the adventitial surface with cushioned forceps, we placed the constrictors and catheters and found that femoral blood flow usually decreased to zero or near-zero over a 3- to 4-minute period. Striking the exposed artery dislodged the obstruction seen on the intravascular ultrasound images and restored flow to normal; spontaneous increases in flow associated with a reopening of the lumen were also noted. After femoral arterial blood flow returned to normal, another cycle of decreasing flow and thrombus formation was spontaneously initiated. Intravascular ultrasound images of thrombus formation were obtained in 18 of 20 experimental procedures, all associated with zero or near-zero arterial flow. Images obtained during spontaneous decreases in femoral artery flow demonstrated the gradual accumulation of material on the lumen. The obstructing thrombus had distinct borders and a "speckled" appearance on ultrasound, especially on dynamic images, which became increasingly bright and uniform with time. At the end of each procedure, the arterial segments were removed for histologic analysis. Gross thrombus was visible in all cases. Therefore, in this experimental model, intravascular ultrasound can successfully detect both the acute formation of thrombus associated with spontaneous episodes of decreased flow and the resolution of thrombus within injured and narrowed femoral arteries. Fresh thrombus has a unique ultrasound pattern that evolves gradually over time.

Balloon aortic valvuloplasty: the Texas Heart Institute experience.

Between October 1986 and January 1989, 73 percutaneous catheter balloon aortic valvuloplasty procedures were performed in 68 adult patients (32 men and 36 women; mean age, 77 +/- 9 years) with severe symptomatic aortic stenosis. Following the procedures, significant improvements were documented in aortic valve area, mean transvalvular pressure gradient, peak-to-peak pressure gradient, left ventricular systolic pressure, radionuclide ejection fraction, and left ventricular end-systolic volume index. There were no procedure-related deaths, but 2 patients (3%) required emergency surgery for acute aortic regurgitation. During hospitalization, 4 patients had persistent symptoms (3 died; 1 subsequently underwent repeat valvuloplasty and later, valve replacement). Short-term clinical improvement was noted in 59 of 65 patients (91%). During the follow-up period (mean, 11.6 +/- 8.4 months), 22 patients died (including the 3 who died during hospitalization). Sixteen underwent aortic valve replacement (including the 2 who underwent emergency aortic valve replacement); all 16 are alive. A total of 6 patients (1 with an initial balloon aortic valvuloplasty at an outside institution) underwent repeat valvuloplasty; of those, 4 subsequently underwent aortic valve replacement, and 2 died. Of the remaining 30 patients, 27 continue to experience relief of symptoms, and 3 have clinical symptoms that have not improved or have worsened since the valvuloplasty procedure. Multivariate predictors of clinical outcome (p<0.05) included post-valvuloplasty aortic valve area, pre- and post-valvuloplasty ejection fraction, absence of coronary artery disease, and absolute change in valve area. Overall actuarial and event-free survivals were 83% and 49%, respectively, at 1 year. Although clinical improvement is frequently noted after balloon aortic valvuloplasty, the procedure is associated with a high recurrence of symptoms and restenosis. Balloon aortic valvuloplasty is at best a palliative procedure; when feasible, surgical valve replacement is the more definitive therapy.

New criteria to increase the reliability of systolic time intervals in left bundle branch block and right ventricular pacing.

We measured the systolic time intervals (STI) in 14 patients (pts) with intermittent left bundle branch block (LBBB) in order to find correlations and comparisons in their values which might pertain to the individual patients, with (b) and without (a) LBBB. QS2I, PEP and the PEP/LVET ratio increased significantly (b) while the LVET I did not change. STI correlation was significant and improved further when the QS2 (b) was corrected by subtracting from it the QRS prolongation (b) in msec. All 7 pts with a PEP/LVET ratio (b) greater than 0.65 had an (a) ratio greater than 0.42 (normal limits for our laboratory), sensitivity 100%. Six of 7 patients with a PEP/LVET (b) less than 0.65 had an (a) ratio less than 0.42 (specificity 87.5%). For the individual patient with LBBB his STI can be quite accurately assessed by subtracting from his QS2 (b) the prolongation of the QRS (b) greater than 80 msec the length of the normal QRS duration. The above data were prospectively evaluated in 10 pts to whom intermittent right ventricular pacing was applied. We found that the correction of the QS2 interval for QRS prolongation permitted a very reliable calculation of the STI.

Comparison of two-dimensional echocardiography, radionuclide ventriculography and cineangiography in detecting surgically documented left ventricular thrombi.

To assess the diagnostic value of various imaging techniques for identifying left ventricular thrombi, we studied 35 patients who underwent left ventricular aneurysm repair and inspection of the ventricular cavity for the presence of a thrombus. All patients underwent preoperative two-dimensional echocardiography and left ventricular cineangiography; radionuclide ventriculography was also performed in 19 of these patients. Data from these procedures were analyzed as in a blind study, and were interpreted as either positive or negative for thrombus. A left ventricular thrombus was present in 22 of the 35 patients at surgery (63%). Two-dimensional echocardiography showed a sensitivity of 95%, specificity of 92% and overall predictive accuracy of 94% for the detection or exclusion of thrombi. In comparison, cineangiography yielded a sensitivity of 73%, specificity of 92% and predictive accuracy of 80%. The sensitivity of radionuclide ventriculography was 60%, specificity was 100%, and predictive accuracy was 79%. Our data, based on a surgical-pathological standard, shows that two-dimensional echocardiography is a highly accurate technique for the diagnosis of left ventricular thrombi, and may be the procedure of choice for this purpose.

Noninvasive assessment of the Ionescu-Shiley pericardial xenograft in the mitral position: preliminary experience.

To establish noninvasive criteria for assessment of the Ionescu-Shiley pericardial xenograft in the mitral position, 29 patients with a normally functioning bioprosthesis were studied with m-mode echocardiography and phonocardiography. Two-dimensional echocardiograms were also obtained in ten of the patients. Although two-dimensional echocardiography provided simultaneous visualization of a greater number of stents and leaflets than the m-mode technique, the superior resolution of m-mode ultrasound permitted more detailed analyses of the xenograft's motion patterns. The anterior leaflet, recorded in all patients, had an average excursion of 1.2 +/- 0.22 cm. Leaflet thickness measured 4 mm or less. Coarse diastolic vibration of the anterior leaflet was recorded in two patients in the absence of both aortic insufficiency and prosthesis dysfunction. Ultrasonic estimates of prosthesis height and orifice diameter did not correlate with micrometer measurements, possibly due to the limited resolution of pulsed ultrasound in the presence of a highly reflective substance. Opening and closing of the pericardial leaflets were associated with the production of high frequency vibrations on the phonocardiogram. The potential usefulness and limitations of echocardiography for evaluating the function of bioprosthetic valves are discussed.

Evidence in man for a fast neural mechanism during the early phase of exercise hyperpnea.

Recently, the rapid increase in ventilation at the onset of exercise has been attributed to reflexes stimulated by the concomitant increase in cardiac output. To evaluate these 'fast-humoral' hypotheses in supine man, the heart rate, ventilation, and end-tidal PCO2 and PO2 were observed during four procedures: the onset of mild dynamic exercise by the lower legs (1) with and (2) without inflation of occluding cuffs around the upper thighs, (3) rapid induction of circulatory occlusion at the level of the upper thighs, and (4) abrupt release of circulatory occlusion after 2.5 min of ischemia. Exercise resulted in abrupt hyperpnea, alveolar hyperventilation, and tachycardia whether or not there was circulatory occlusion. Circulatory occlusion engendered abrupt bradycardia and transient, hyperventilatory hyperpnea. Release of circulatory occlusion resulted in relatively large tachycardia and, after a delay, small hyperpnea and alveolar hypoventilation. The results demonstrate that the early response to exercise is not inherently isocapnic hyperpnea and that, contrary to the prediction of the fast-humoral hypotheses, the presumed increase in cardiac output following cuff release does not produce a ventilatory response similar to that of exercise. These findings support the existence of a neurally mediated factor during the early stages of exercise hyperpnea.

RIGHT AND LEFT VENTRICULAR HEMODYNAMIC INDICES AS PREDICTORS OF THE NEED FOR AND OUTCOME OF POST-CARDIOTOMY MECHANICAL INTRAAORTIC BALLOON PUMP SUPPORT.

Preoperative cardiac catheterization data of 21 patients requiring intraaortic balloon pumping (IABP) for weaning from cardiopulmonary bypass were analyzed and compared with similar data in 28 patients who underwent nearly similar operative procedures, but did not require IABP for weaning. Cardiac index (CI) and systemic vascular resistance (SVR) were found to have predictive value for the need of IABP for weaning from cardiopulmonary bypass and differentiated survival from non-survival. Left ventricular end diastolic pressure (LVEDP) was not found to be predictive. Ejection fraction (EF) was significantly lower in those who required IABP than those who did not; EF did not predict the outcome. Pulmonary capillary wedge pressure ([unk]), pulmonary artery pressure ([unk]) and pulmonary vascular resistance (PVR) were predictive of the need for IABP, but not the outcome. Left ventricular minute work index (LVMWI) was significantly lower in those requiring IABP, right ventricular minute work index (RVMWI) was predictive of survival with IABP. Together, LVMWI and RVMWI were predictive of the need for and outcome of IABP following cardiopulmonary bypass. Twenty-seven of 28 control RVMWI's were normal. No patient requiring IABP had depressed RVMWI's preoperatively. Elevated preoperative RVMWI's were associated with 80% survival with postcardiotomy IABP; normal RVMWI's were associated with a 56% survival with post-cardiotomy IABP. Elevated preoperative RVMWI's reflected moderate to maximal right ventricular compensatory capacity in response to depressed left ventricular function. Normal preoperative RVMWI's in the presence of depressed LVMWI's were indicative of decreased right ventricular compensatory capacity in post-cardiotomy IABP-support settings. Right ventricular function is as important as left ventricular function as a prognosticator for the need and outcome of IABP support of the failing post-cardiotomy circulation.