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Biomedical subjects

P C Block

Publications and source records attributed to P C Block.

At least 73 records · Page 4Linked to original sources
PubMed1989

Cardiac conduction abnormalities during percutaneous balloon mitral or aortic valvotomy.

To evaluate the electrophysiologic changes in the cardiac conduction system that occur during percutaneous mitral or aortic balloon valvotomy, we prospectively studied the conduction system in 19 patients (10 mitral, 8 aortic, and 1 both) undergoing this procedure. A His bundle electrogram was recorded in all patients, and when sinus rhythm was present, the atrioventricular (AV) node effective refractory period was measured. Holter monitoring was performed during and for 24 hours after the procedure. Follow-up electrocardiograms (ECG) were available in 11 patients 2.3 +/- 1.5 months after the procedure. The AV node effective refractory period before (276 +/- 86 msec) and after valvotomy (298 +/- 85 msec) were not significantly different. The maximum His-Purkinje conduction time (HV interval) observed during valvotomy (66 +/- 20 msec) was significantly longer (p less than 0.01) than that measured before (57 +/- 10 msec) or after (60 +/- 18 msec) valvotomy. The mean HV intervals before and after valvotomy were not significantly different. The mean QRS complex duration increased from 95 +/- 28 to 112 +/- 28 msec during valvotomy and remained significantly prolonged (109 +/- 26 msec) 24 hours after the procedure (p less than 0.01). A new intraventricular conduction defect (QRS complex duration greater than 100 msec) or bundle branch block occurred in five of 13 patients who had normal QRS duration before the procedure. The change in HV interval did not correlate with the change in QRS complex duration. In four patients, the newly acquired intraventricular conduction defect was still present on follow-up ECG tracing. Complete heart block was not observed in any patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Octogenarians with aortic stenosis. Outcome after aortic valve replacement.

To assess the outcome of aortic valve replacement for aortic stenosis in octogenarians, we retrospectively studied 64 patients, aged 80-89 years, who underwent aortic valve replacement for aortic stenosis from 1974 to 1987. Mean aortic valve gradient was 61 +/- 22 mm Hg, and valve area was 0.5 +/- 0.2 cm2. Concurrent coronary artery bypass grafting was performed in 29 patients, mitral valve replacement in two, and both procedures in two. Serious, comorbid, noncardiac conditions were infrequent. In-hospital mortality was 9.4%. Outcomes were classified as 1a) uncomplicated; 1b) complicated (technically complicated surgery, temporary encephalopathy, discharge to a rehabilitation facility, or some combination thereof) but with ultimately good results; or 2) unfavorable (death or permanent, severe neurological deficit). There were 28 (44%) patients in group 1a, 24 (38%) in group 1b, and 12 (19%) in group 2. Of 18 patients with preoperative left ventricular ejection fraction less than 50%, two (11%) were in group 2. Of 31 patients undergoing aortic valve replacement only, two (6%) were in group 2, compared with 10 of 33 (30%) patients who had concomitant coronary artery bypass grafting, mitral valve replacement, or both (p = 0.02). Late follow-up at 28 +/- 5 months revealed four cardiac and seven noncardiac deaths, with actuarial 1- and 5-year survival rates of 83 +/- 5% and 67 +/- 10%, respectively. With few exceptions, survivors were free of cardiac symptoms. Thus, short- and long-term outcomes after aortic valve replacement for aortic stenosis in otherwise healthy octogenarians is generally favorable, even in the presence of preoperative left ventricular systolic dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1988

A prospective randomized trial of outpatient versus inpatient cardiac catheterization.

To evaluate the safety and cost of outpatient cardiac catheterization, we conducted a randomized trial at three hospitals of outpatient (n = 192) as compared with inpatient (n = 189) cardiac catheterization in low-risk patients. Outpatients had the following complication rates as compared with inpatients: hematoma, 12 versus 8.5 percent; numbness or weakness of extremity, 0.5 versus 1.6 percent; cold or blue extremity, 1.6 versus 1.1 percent; and acute myocardial infarction, 1.6 versus 0.5 percent. None of these differences were statistically significant. No deaths or strokes occurred in either group. Twenty-three patients (12 percent) assigned to the outpatient group required hospitalization because of complications of catheterization. In the outpatient group, the relative risk for hematoma was 1.42 (95 percent confidence interval, 0.77 to 2.29), and the relative risk for myocardial infarction within one week was 2.95 (95 percent confidence interval, 0.3 to 28.1). There were no significant differences between the two groups in whether they resumed normal activities or in the rates of rehospitalization within one week of the procedure. Total catheterization-related charges per patient were $679 lower for outpatients, with a savings in total hospital charges (including charges for subsequent therapeutic procedures) of $885 per patient. We conclude that elective cardiac catheterization as an outpatient procedure for selected patients is feasible and safe. Given the small size of our sample, however, we urge caution in interpreting these findings, since they do not exclude a small increase in complication rates with outpatient cardiac catheterization.

Ambulatory Care↗
PubMed1988

Clinical and hemodynamic follow-up after percutaneous aortic valvuloplasty in the elderly.

This study reports clinical (84 patients) and catheterization (15 patients) follow-up of the first 90 patients who underwent percutaneous balloon aortic valvuloplasty (PBAV) at Massachusetts General Hospital. Eight patients died within 1 week in-hospital; 1 patient was lost to follow-up. Mean age of the group was 79 +/- 1 year (range 52 to 95). Before PBAV 25% of the patients were in New York Heart Association class III and 73% were in class IV. Endpoints were aortic valve surgery, death, second PBAV or interview. Mean follow-up was 5.5 +/- 0.3 months after PBAV. Although all patients improved symptomatically immediately after PBAV, at follow-up 16% were in New York Heart Association class I, 20% were in class II, 11% were in class III and 25% were in class IV. Twenty-three (28%) patients died during the follow-up period. A second PBAV was performed in 15 patients who had repeat catheterization. All had restenosis but only 13 of 15 had recurrent symptoms. Repeat PBAV produced results similar to the first PBAV despite the use of larger or double balloons. Although PBAV improves most patients' symptoms, recurrence of clinical symptoms and a high mortality within 6 months should limit the procedure to selected patients.

Aged↗
PubMed1988

Percutaneous mitral balloon valvotomy during pregnancy in a patient with severe mitral stenosis.

Percutaneous mitral balloon valvotomy (PMV) was performed successfully in a 41-year-old pregnant patient with severe mitral stenosis. The patient had a 21-week gestation and was severely limited by symptoms resulting from critical mitral stenosis. PMV resulted in a decrease in the diastolic mitral gradient from 26 to 2 mm Hg and an increase in both cardiac output (from 4.2 to 5.7 l/min) and mitral valve area (from 0.7 to 3.7 cm2). She had marked symptomatic improvement, no further heart failure, and a full-term, normal delivery. This case report indicates that PMV may be the treatment of choice in the management of pregnant patients with incapacitating symptoms caused by severe mitral stenosis.

Adult↗
PubMed1988

Mitral balloon valvuloplasty for mitral restenosis after surgical commissurotomy.

Mitral balloon valvuloplasty was performed in 14 patients with recurrent mitral stenosis 16.9 +/- 1.8 years (range 6 to 30) after surgical commissurotomy. There were 13 women and 1 man with a mean age of 55 +/- 4 years (range 23 to 73). Mitral balloon valvuloplasty resulted in an increase in mitral valve area from 0.8 +/- 0.1 to 1.7 +/- 0.2 cm2 (p = 0.001), a decrease in mean mitral diastolic pressure gradient from 15 +/- 2 to 7 +/- 1 mm Hg (p = 0.001) and an increase in cardiac output from 3.4 +/- 0.3 to 3.9 +/- 0.3 liters/min (p = 0.03). No deaths, strokes, vascular complications or conduction abnormalities were observed. Mitral regurgitation developed or increased in severity in seven patients (50%). There was no evidence of significant left to right shunt through the atrial septal puncture site after mitral balloon valvuloplasty. A good result (defined as a mitral valve area greater than 1.0 cm2, an increase in mitral valve area greater than 25% and a mean gradient less than 10 mm Hg) was achieved in 9 (64%) of the 14 patients. A subgroup of four patients who had a superior result (increase in mitral valve area of 1.7 +/- 0.2 versus 0.5 +/- 0.1 cm2 in the other 10 patients, p = 0.004) was identified. These patients had less echocardiographic evidence of rheumatic mitral valve damage and were the only patients who had sinus rhythm. They were also younger, less debilitated and had a lower grade of fluoroscopic valve calcification compared with the other patients. Thus, mitral balloon valvuloplasty is a safe and effective procedure for patients with recurrent mitral stenosis after surgical commissurotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Mitral regurgitation after percutaneous balloon mitral valvuloplasty in adults: evaluation by pulsed Doppler echocardiography.

Percutaneous balloon mitral valvuloplasty is a new technique used in the treatment of adult patients with mitral stenosis. To evaluate the occurrence and severity of mitral regurgitation after balloon valvuloplasty, 24 patients (20 women and 4 men, mean age 57 years) were studied using two-dimensional and Doppler echocardiography before and less than 24 h after this procedure. Mitral valve area increased after valvuloplasty in all patients, from 0.89 +/- 0.07 to 1.61 +/- 0.09 cm2 (p less than 0.001). Before valvuloplasty, 10 patients had no mitral regurgitation, 4 had 1+, 4 had 2+ and 6 had 3+ mitral regurgitation. After valvuloplasty, new mitral regurgitation occurred in six patients. Regurgitation grade did not change in 13 patients (54%), increased by one grade in 8 patients (33%) and by two grades in 3 patients (13%). Left atrial volume decreased in all except one patient from 100 +/- 12 to 83 +/- 12 cm3 (p less than 0.001). Neither age, sex, cardiac rhythm, initial mitral valve area, increase in mitral valve area, morphologic characteristics of the valvular and subvalvular apparatus, previous mitral commissurotomy nor effective balloon dilating area discriminated between those patients with and without an increase in mitral regurgitation after valvuloplasty. Thus, mitral balloon valvuloplasty is frequently associated with an increase in mitral regurgitation. However, in this series, no patient developed severe mitral regurgitation, and left atrial volume decreased in nearly all patients. An increase in mitral regurgitation could not be predicted from any features of the valve or subvalvular apparatus, clinical characteristics of the patients or technical aspects of the procedure.

Adult↗
PubMed1988

Echocardiographic evaluation of mitral valve structure and function in patients followed for at least 6 months after percutaneous balloon mitral valvuloplasty.

Although beneficial results have been reported immediately after percutaneous mitral balloon valvuloplasty, little information is available concerning the longer-term outcome of this procedure. The anatomic and functional results of percutaneous mitral valvuloplasty were assessed in 20 patients, in whom two-dimensional and Doppler echocardiographic examination could be obtained both immediately and 6 to 11 months (mean 7.5 +/- 2.0) after balloon dilation. Mean valve area measured by planimetry decreased slightly but significantly from 1.90 +/- 0.59 cm2 immediately after valvuloplasty to 1.62 +/- 0.55 cm2 (p less than 0.001) at follow-up. Individual changes in valve area were variable, and in four patients valve area decreased by greater than 25%. Echocardiographic scores of valvular morphology were obtained by assigning scores of 0 to 4 (with increasing abnormality) to each of four morphologic characteristics of the valve, namely, leaflet mobility, thickening, calcification and subvalvular thickening. This score was higher in the four patients with a decrease in valve area greater than 25% at follow-up than in the other patients (11 +/- 2 versus 7 +/- 2, p less than 0.002). Multiple regression analysis of several hemodynamic and echocardiographic factors identify first the echocardiographic score and second the valve area postvalvuloplasty as the only significant predictors of the percent decrease in valve area (r = 0.70, p less than 0.006). Mitral regurgitation graded by pulsed Doppler ultrasound decreased from 1.9 +/- 1.2 immediately after valvuloplasty to 1.0 +/- 0.9 (p less than 0.003) at follow-up, whereas there was no change in mean transmitral pressure gradient by Doppler echocardiography (5 +/- 2 versus 6 +/- 3 mm Hg, p = NS) and left atrial volume (74 +/- 34 versus 72 +/- 27 cm3, p = NS). Thus, 6 to 11 months after balloon mitral valvuloplasty, mean mitral valve area decreases slightly. Individual changes in valve area, however, are variable. Valvular morphology assessed by two-dimensional echocardiography may be useful for identifying those patients who have an increased likelihood of developing valvular restenosis.

Adult↗
PubMed1988

Responsiveness of plasma atrial natriuretic factor to short-term changes in left atrial hemodynamics after percutaneous balloon mitral valvuloplasty.

To assess the effect of short-term alteration of left atrial pressure and volume on the circulating plasma level of atrial natriuretic factor, 11 patients with left atrial hypertension due to mitral stenosis were studied at the time of percutaneous balloon mitral valvuloplasty. Hemodynamic measurements and plasma atrial natriuretic factor levels were obtained before, immediately (5 to 10 min) after and 24 h after valvuloplasty, and echocardiographic left atrial size was determined before and 24 h after valvuloplasty. Immediately after valvuloplasty, left atrial pressure decreased from 28 +/- 2 to 10 +/- 1 mm Hg (p less than 0.0005), mitral pressure gradient decreased from 20 +/- 2 to 7 +/- 1 mm Hg (p less than 0.0005), mitral valve area increased from 0.8 +/- 0.1 to 1.9 +/- 0.2 cm2 (p less than 0.0005) and plasma atrial natriuretic factor level rose from 249 +/- 42 to 348 +/- 50 pg/ml (p less than 0.01). This short-term rise in atrial natriuretic factor level may reflect a transient increase in left atrial pressure associated with balloon occlusion of the mitral valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Percutaneous balloon dilatation of the mitral valve: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation.

Twenty two patients (four men, 18 women, mean age 56 years, range 21 to 88 years) with a history of rheumatic mitral stenosis were studied by cross sectional echocardiography before and after balloon dilatation of the mitral valve. The appearance of the mitral valve on the pre-dilatation echocardiogram was scored for leaflet mobility, leaflet thickening, subvalvar thickening, and calcification. Mitral valve area, left atrial volume, transmitral pressure difference, pulmonary artery pressure, cardiac output, cardiac rhythm, New York Heart Association functional class, age, and sex were also studied. Because there was some increase in valve area in almost all patients the results were classified as optimal or suboptimal (final valve area less than 1.0 cm2, final left atrial pressure greater than 10 mm Hg, or final valve area less than 25% greater than the initial area). The best multiple logistic regression fit was found with the total echocardiographic score alone. A high score (advanced leaflet deformity) was associated with a suboptimal outcome while a low score (a mobile valve with limited thickening) was associated with an optimal outcome. No other haemodynamic or clinical variables emerged as predictors of outcome in this analysis. Examination of pre-dilatation and post-dilatation echocardiograms showed that balloon dilatation reliably resulted in cleavage of the commissural plane and thus an increase in valve area.

Adult↗
PubMed1988

Transcatheter closure of ventricular septal defects.

Between January and October, 1987, we attempted percutaneous transcatheter closure of seven ventricular septal defects (VSD) in six patients; none of the patients was a candidate for operative management. Patients' ages ranged from 8 months to 82 years (6.0-70 kg); diagnoses included postinfarction VSD (n = 4), congenital VSD (n = 1), and postoperative congenital VSD (n = 2). Indications for VSD closure were shock or respiratory failure (n = 5) or multiple episodes of endocarditis (n = 1). Closure was attempted with a Rashkind double umbrella: VSDs were crossed via the left ventricle and a guide wire was advanced to the right heart, snared with a venous catheter, and used to direct a long sheath (and ultimately the double umbrella) across the VSD. We crossed the VSD in all seven attempts, and a 17-mm double umbrella was successfully placed in each VSD. In the first (postinfarction) patient with the largest (12 mm) VSD, the umbrella embolized after 20 seconds to the pulmonary artery (without reducing flow). The other six umbrellas remained in position, either diminishing or abolishing the left-to-right shunts. Postinfarction patients had increasing VSD shunting over the next several days and died; at postmortem, the umbrellas remained well positioned in the septum, with other VSDs present. All three congenital VSDs had absent or diminished shunts after umbrella closure. These preliminary data indicate that transcatheter VSD closure is feasible in selected cases.

Angiography↗
PubMed1988

Inaccuracy of mitral pressure half-time immediately after percutaneous mitral valvotomy. Dependence on transmitral gradient and left atrial and ventricular compliance.

Mitral pressure half-time (T1/2) is widely used as an independent measure of mitral valve area in patients undergoing percutaneous mitral valvotomy. However, fluid dynamics theory predicts T1/2 to be strongly dependent on chamber compliance and the peak transmitral gradient, which are variables that change dramatically with valvotomy. These theoretical predictions were tested in an in vitro model of the left heart where valve area, chamber compliance, and initial gradient were independently adjusted. Measured T1/2 was observed to vary inversely with orifice area and directly with net chamber compliance and the square root of the initial pressure gradient. Theoretical predictions of T1/2 agreed with observed values with r = 0.998. To test this theory in vivo, the hemodynamic tracings of 18 patients undergoing mitral valvotomy were reviewed. Predictions were made for T1/2 assuming dependence only on valve area; these showed some correlations before valvotomy (r = 0.48-0.64, p less than 0.05) but none after valvotomy (r = 0.05-0.28, p = NS). Predictions for T1/2 based on the theoretical derivation (and thus including compliance and pressure in their calculation) were much better: before valvotomy, r = 0.93-0.96, p less than 0.0001; after valvotomy, r = 0.52-0.66, p less than 0.05. These data indicate that T1/2 is not an independent inverse measure of mitral valve area but is also directly proportional to net chamber compliance and the square root of the initial transmitral gradient. These other factors render T1/2 an unreliable measure of mitral valve area in the setting of acute mitral valvotomy.

Catheterization↗
PubMed1988

Percutaneous balloon mitral valvotomy for patients with mitral stenosis. Analysis of factors influencing early results.

Percutaneous balloon mitral valvotomy has recently been developed as an alternative to surgical commissurotomy for patients with rheumatic mitral stenosis. We analyzed our initial experience with 60 consecutive procedures performed in 49 patients over 1 1/2 years and identified factors influencing the immediate hemodynamic results. For the total patient population, the mitral valve area increased after percutaneous mitral valvotomy from 0.8 +/- 0.04 to 1.6 +/- 0.11 cm2 (p less than 0.001). Mean diastolic mitral gradient fell from 18 +/- 1 to 7 +/- 0.4 mm Hg (p less than 0.001), and cardiac output increased from 3.8 +/- 0.2 to 4.5 +/- 0.2 L/min (p less than 0.01). Although percutaneous mitral valvotomy resulted in an increase in mitral valve area in each patient, a suboptimal result, as defined by a postprocedure mitral valve area of 1.0 cm2 or less, an increase in area of 25% or less, or a final mitral gradient of 10 mm Hg or more occurred in 21 of the 60 procedures (35%). Multivariate analysis of 16 variables was performed to determine which factors might predict this result. Patients with a suboptimal result were more likely to have severe valve leaflet thickening or immobility and an extreme degree of subvalvular thickening and calcification on echocardiogram. Other factors that predicted a suboptimal result were a smaller effective balloon dilating area and the presence of atrial fibrillation. Thus optimal immediate hemodynamic results can be obtained in the majority of patients undergoing percutaneous mitral valvotomy. Optimal results may be expected in patients in normal sinus rhythm, with pliable mitral leaflets, and with no severe subvalvular disease identified by echocardiography, who undergo dilation with large effective balloon dilating areas.

Catheterization↗
PubMed1988

Pulmonary vascular dynamics after percutaneous mitral valvotomy.

Hemodynamic studies were performed immediately before, within 1/2 hour, and every 8 hours for 24 hours after percutaneous mitral valvotomy in 22 patients with severe mitral stenosis and pulmonary hypertension. The mean pressure in the left atrium decreased from 27 +/- 2 mm Hg to 14 +/- 1 mm Hg (p less than 0.01) immediately after successful valvotomy. There was no significant further drop in left atrial pressure (or pulmonary capillary wedge pressure) over 24 hours. Mean cardiac output increased from 3.9 +/- 0.3 L/min to 4.6 +/- 0.3 L/min immediately after successful valvotomy (p less than 0.01). Cardiac output continued to rise for the next 8 hours and plateaued during the 24-hour period of observation. Pulmonary vascular resistance dropped immediately after the relief of mitral valve obstruction in all patients. In the group of patients who had elevated pulmonary vascular resistance after valvotomy, resistance continued to drop significantly (p less than 0.05) over the next 24 hours. In some cases it did not fall to normal levels despite adequate relief of mitral stenosis.

Adult↗
PubMed1987

Comparison of hemodynamic results of anterograde versus retrograde percutaneous balloon aortic valvuloplasty.

Percutaneous balloon aortic valvuloplasty (PAV) has been reported in children and in selected adults with aortic stenosis using retrograde arterial catheterization. Some patients, however, cannot undergo retrograde catheterization because of atherosclerotic disease, previous vascular surgery or the presence of vessel tortuosity. Because PAV requires the use of large balloon dilating catheters, extreme bleeding and local arterial damage are potential complications. The results of PAV using the anterograde transseptal approach were compared with those using the retrograde arterial approach. Diminution in aortic gradient and increase in aortic valve area were similar in the 2 groups. Vascular complications were more common using the retrograde approach (4 vs 0). Thus, PAV can be performed successfully using anterograde transseptal catheterization. This technique of PAV could be particularly useful in patients who cannot undergo retrograde arterial catheterization.

Aged↗
PubMed1987

Degree of reversibility of left ventricular systolic dysfunction after aortic valve replacement for isolated aortic valve stenosis.

To determine whether a low preoperative left ventricular (LV) ejection fraction (EF) returns to normal late after aortic valve replacement for aortic stenosis, 42 patients with critical aortic stenosis (valve area 0.7 cm2 or less), LV systolic dysfunction (EF 0.45 or less), angiographically normal coronary arteries, and no other significant valvular disease were studied at 10 to 84 months (mean 41 +/- 21) postoperatively. All patients survived aortic valve replacement and were discharged clinically improved. There were 4 late deaths; these patients were older (79 +/- 6 vs 64 +/- 13 years, p = 0.007) and had lower preoperative mean valve gradients (51 +/- 6 vs 68 +/- 23 mm Hg, p = 0.003) than late survivors. Of 23 survivors who returned for follow-up radionuclide angiography and Doppler echocardiography, 21 were asymptomatic. EF returned to normal (0.50 or more) in 14 patients (group 1) and remained low in 9 patients (group 2). Doppler peak prosthetic valve gradient was 24 +/- 8 mm Hg in group 1 and 25 +/- 10 mm Hg in group 2 (difference not significant). Six of the 9 patients in group 2 underwent early postoperative radionuclide imaging, and LVEF was normal in 4 (0.65 +/- 0.14 early vs 0.41 +/- 0.06 late, p = 0.02). Of 77 preoperative and intraoperative variables analyzed, only paroxysmal nocturnal dyspnea (0 of 14 vs 4 of 9, p = 0.01) distinguished group 1 from group 2. Thus, LVEF does not always normalize after aortic valve replacement for AS, implying impaired myocardial contractility.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗