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Biomedical subjects

P C Block

Publications and source records attributed to P C Block.

At least 37 records · Page 2Linked to original sources
PubMed1997

The effects of folic acid supplementation on plasma total homocysteine are modulated by multivitamin use and methylenetetrahydrofolate reductase genotypes.

Elevated concentration of plasma total homocysteine (tHcy) is a common risk factor for arterial occlusive diseases. Folic acid (FA) supplementation usually lowers tHcy levels, but initial tHcy and vitamin levels, multivitamin use, and polymorphisms in the gene for 5, 10-methylenetetrahydrofolate reductase (MTHFR) may contribute to variability in reduction. We tested the effects of a 3-week daily intake of 1 or 2 mg of FA supplements on tHcy levels in patients with and without coronary heart disease (CHD) who were analyzed for the C677T MTHFR mutation. Prior multivitamin intake and baseline vitamin and tHcy levels were also compared with responsiveness to folate supplementation. Both dosages of FA lowered tHcy levels similarly, regardless of sex, age, CHD status, body mass index, smoking, or plasma creatinine concentration. In non-multivitamin users, FA supplements reduced tHcy by 7% in C/C homozygotes and by 13% or 21% in subjects with one or two copies of the T677 allele, respectively; the corresponding reductions were smaller in users of multivitamins. Moreover, T/T homozygotes had elevated tHcy and increased susceptibility to high levels of tHcy at marginally low plasma folate levels, as well as enhanced response to the tHcy-lowering effects of FA. Although other factors are probably involved in the responsiveness of tHcy levels to FA supplementation, about one third of heterogeneity in responsiveness was attributable to baseline tHcy and folate levels and to multivitamin use.

Alleles↗
PubMed1995

Imaging and sizing of atrial septal defects by magnetic resonance.

BACKGROUND: Development of techniques for percutaneous closure of atrial septal defects (ASDs) makes accurate noninvasive sizing of ASDs important for appropriate patient selection. METHODS AND RESULTS: Magnetic resonance (MR) images of ASDs were obtained in 30 patients (mean age, 41 +/- 16 years) by both spin-echo and phase-contrast cine MR imaging. Spin-echo images were obtained in two orthogonal views (short-axis and four-chamber) perpendicular to the plane of the ASD. Spin-echo major and minor diameters were measured, and spin-echo defect area was calculated. Phase-contrast cine MR images were obtained in the plane of the ASD, and cine major diameter and defect area were measured from the region of signal enhancement or phase change due to shunt flow across the defect. MR measurements were compared with templates cut during surgery to match the defect or with ASD diameter determined by balloon sizing at catheterization. ASD size measured from cine MR images (y) agreed closely with catheterization and template standards (x). For major diameter, y = 0.78x + 5.7, r = .93, and SEE = 3.4 mm. On average, spin-echo measurements overestimated major diameter and area of secundum ASDs by 48% and 125%, respectively. CONCLUSIONS: Phase-contrast cine MR images acquired in the plane of an ASD define the defect shape by the cross section of the shunt flow stream and allow noninvasive determination of defect size with sufficient accuracy to permit stratification of patients to closure of the defect by catheter-based techniques versus surgery. Spin-echo images, on the other hand, are not adequate for defining ASD size, because septal thinning adjacent to a secundum ASD may appear to be part of the defect.

Adult↗
PubMed1995

Percutaneous mitral balloon valvotomy for recurrent mitral stenosis after surgical commissurotomy.

Immediate outcome and 4-year follow-up results of percutaneous mitral balloon valvotomy (PMV) in patients with previous surgical mitral commissurotomy are studied. Repeat surgical mitral commissurotomy in patients with previous surgical commissurotomy is associated with higher mortality and morbidity. PMV has been proven to be safe and could be an ideal alternative in this patient group. The results of 68 patients with previous surgical commissurotomy were compared with those of 261 patients without prior surgical intervention. A good outcome, defined as the final mitral valve area > 1.5 cm2, was obtained in 51% of the patients with prior surgical commissurotomy compared with 71% in the control group (p = 0.002). During the 4-year follow-up period, there were more patients who required mitral valve replacement (19% vs 7%; p = 0.004) and who were in New York Heart Association functional class III and IV (85% vs 71%; p = 0.02) among those with prior surgical commissurotomy. However, when these patients were divided according to echocardiographic score, those with a score < or = 8 had immediate outcome and long-term results similar to those without prior commissurotomy. PMV can be performed safely in patients with prior surgical commissurotomy. Although results of long-term follow-up in these patients is not as good as those in patients without prior surgical commissurotomy, those with a low echocardiographic score had similar excellent long-term results.

Adult↗
PubMed1995

Clinical follow-up of patients undergoing percutaneous mitral balloon valvotomy.

BACKGROUND: This study is the clinical follow-up (20 +/- 12 months; range, 6 to 49 months) of 327 patients who had percutaneous mitral balloon valvotomy (PMV) at the Massachusetts General Hospital. METHODS AND RESULTS: There were seven in-hospital deaths. Patients were divided into two groups according to their echocardiographic score; 211 patients had echocardiographic scores < or = 8 and 116, echocardiographic scores > 8. Patients with echocardiographic scores > 8 were older (64 +/- 11 versus 48 +/- 14 years, P < .01), and more had atrial fibrillation (65% versus 40%, P < .01), calcium under fluoroscopy (81% versus 29%, P < .01), and previous surgical commissurotomy (30% versus 16%, P < .01) than patients with echocardiographic scores < or = 8. With PMV, mitral valve area increased from 1.0 +/- 0.3 to 2.2 +/- 0.8 cm2 in patients with echocardiographic scores < or = 8 and from 0.8 +/- 1 to 1.7 +/- 0.7 cm2 in those with echocardiographic scores > 8. Rates of survival (98 +/- 2% versus 72 +/- 11%), survival with freedom from mitral valve replacement (91 +/- 4% versus 55 +/- 13%), and survival with freedom from combined events (79 +/- 10% versus 39 +/- 18%) at follow-up were greater in patients with echocardiographic scores < or = 8 (P < .00005). Cox regression analysis identified the echocardiographic score as the most important unfavorable intermediate long-term follow-up prediction factor after PMV. CONCLUSIONS: The excellent intermediate long-term clinical follow-up of patients with echocardiographic score < or = 8 and no calcified mitral valves suggests that PMV may be the treatment of choice in this group of patients.

Adolescent↗
PubMed1995

Major determinants of survival and nonsurvival of intraaortic balloon pumping.

The purpose of this study was to find the major determinants of survival and nonsurvival after intraaortic balloon pump (IABP) support. One hundred twenty-nine consecutive patients with IABP support from January 1988 to January 1992 were analyzed retrospectively. Differences between the survival and nonsurvival groups were tested with the Student's t test, chi-squared test, and frequency analysis. The overall survival rate was 50.4% (65 of 129). Nonsurvivors (64 of 129, 49.6%) had higher rates of chronic heart failure (21.9% vs 9.2%, p < 0.05), acute myocardial infarction (53.1% vs 24.6%, p < 0.01), cardiomyopathy (9.4% vs 1.5%, p < 0.05), New York Heart Association functional class IV (51.6% vs 13.9%, p < 0.01), and depressed left ventricular ejection fraction (29.38% +/- 8.99% vs 42.88% +/- 5.24%, mean +/- SD, p < 0.01). The nonsurvival group also had longer duration of cardiopulmonary bypass (115.80 +/- 24.43 vs 78.34 +/- 3.81 min, mean +/- SEM, p < 0.02) and aortic occlusion (57.55 +/- 13.03 vs 41.00 +/- 2.79 min, mean +/- SEM, p < 0.05) than the survival group. The major determinants of death after IABP are acute myocardial infarction, left ventricular ejection fraction < 30%, New York Heart Association functional class IV, and longer duration of cardiopulmonary bypass and aortic occlusion. IABP is effective in sustaining hemodynamics, but severe myocardial pump failure portends a poor treatment outcome.

Adolescent↗
PubMed1994

Percutaneous double balloon valvotomy for bioprosthetic tricuspid stenosis.

We report two cases of percutaneous balloon valvotomy of porcine tricuspid valves and review the brief literature. Both procedures were successful, but "restenosis" resulted in tricuspid valve replacement in patient 2. The explanted valve showed leaflet thickening and calcified cuspal nodules. Patient 1 is improved 10 months later.

Adult↗
PubMed1994

The role of percutaneous aortic balloon valvuloplasty in patients with cardiogenic shock and critical aortic stenosis.

OBJECTIVES: The goal of this study was to evaluate the role of percutaneous aortic valvuloplasty in patients with cardiogenic shock due to severe aortic stenosis and associated major comorbid conditions and to establish predictors of survival. BACKGROUND: The prognosis for patients in cardiogenic shock with severe aortic stenosis is poor. Aortic valve replacement can be lifesaving, but the presence of multiorgan failure precludes these patients from operation. Percutaneous aortic balloon valvuloplasty has been used in these patients with short-term improvement and could be an alternative therapeutic option. METHODS: Of 310 patients undergoing percutaneous aortic balloon valvuloplasty, 21 were in cardiogenic shock and were included in this study. All 21 patients had associated major comorbid conditions at the time of presentation. RESULTS: After percutaneous aortic balloon valvuloplasty, systolic aortic pressure increased from 77 +/- 3 (mean +/- SEM) to 116 +/- 8 mm Hg (p = 0.0001); aortic valve area increased from 0.48 +/- 0.04 to 0.84 +/- 0.06 cm2 (p = 0.0001); and cardiac index increased from 1.84 +/- 0.13 to 2.24 +/- 0.15 liters/min per m2 (p = 0.06). Nine patients died in the hospital, two during the procedure and seven after successful percutaneous aortic balloon valvuloplasty (five from multiorgan failure). Five patients had vascular complications. Stroke, cholesterol emboli and aortic regurgitation requiring aortic valve replacement occurred in one patient each. Twelve patients (57%) survived and were followed up for 15 +/- 6 months; five patients subsequently died. The Kaplan-Meier survival curve showed a 38 +/- 11% survival rate at 27 months. The only predictor for longer survival rate was the postprocedure cardiac index. CONCLUSIONS: 1) Emergency percutaneous aortic balloon valvuloplasty can be performed successfully as a lifesaving procedure. 2) Morbidity and mortality remain high despite successful percutaneous aortic balloon valvuloplasty. 3) For nonsurgical candidates, percutaneous aortic balloon valvuloplasty may be the only therapeutic alternative.

Adult↗
PubMed1994

Percutaneous mitral balloon valvotomy in patients with calcific mitral stenosis: immediate and long-term outcome.

OBJECTIVES: This study analyzed the immediate and long-term outcome of percutaneous balloon mitral valvotomy in patients with and without fluoroscopically visible mitral valve calcification. BACKGROUND: Mitral valve calcification has been shown to be an important factor in determining immediate and long-term outcome of patients undergoing surgical mitral commissurotomy. Patient selection has an important impact on the outcome of percutaneous balloon mitral valvotomy. METHODS: The immediate and long-term results of percutaneous balloon mitral valvotomy were compared in 155 patients with and 173 patients without mitral valve calcification. The patients with calcified valves were assigned to four groups according to severity of calcification. RESULTS: Patients with calcified mitral stenosis more frequently were in New York Heart Association functional class III or IV and more frequently had atrial fibrillation, previous surgical commissurotomy, echocardiographic score > 8, higher pulmonary artery and left atrial pressures, higher pulmonary vascular resistance and mean mitral valve gradient and lower cardiac output and smaller mitral valve area. Mitral valve area after valvotomy was significantly smaller in patients with calcified valves (1.8 +/- 0.06 vs. 2.1 +/- 0.06 cm2) and was > or = 1.5 cm2 in 65% of patients with and 83% of patients without calcified valves (p = 0.004). A successful outcome, defined as mitral valve area > 1.5 cm2 without significant mitral regurgitation and left to right shunting, was achieved in 52% of patients with and 69% of patients without uncalcified valves (p = 0.001). The success rate was 59%, 48%, 35% and 33% in subgroups with 1+, 2+, 3+ and 4+ calcification, respectively. The rates of significant left to right shunting and mitral regurgitation after valvuloplasty were similar in the two groups. Estimated survival rate (80% vs. 99%, respectively, p = 0.0001), survival rate without mitral valve replacement (67% vs. 93%, respectively, p < 0.00005) and event-free survival rate (63% vs. 88%, respectively, p < 0.00005) at 2 years were significantly better in the patients with uncalcified valves. Survival rate curves became progressively worse as the severity of calcification increased. CONCLUSIONS: These findings indicate that immediate and long-term results of mitral valvuloplasty are not as successful in patients with fluoroscopically visible mitral valve calcification as in those without calcification.

Calcinosis↗
PubMed1994

Three-year outcome after balloon aortic valvuloplasty. Insights into prognosis of valvular aortic stenosis.

BACKGROUND: To identify predictors of long-term outcome after balloon aortic valvuloplasty, we analyzed data on 674 adults (mean age, 78 +/- 9 years; 56% were women) undergoing this procedure at 24 clinical centers who had a mean initial increase in aortic valve area of 0.3 cm2. METHODS AND RESULTS: Baseline data included clinical, echocardiographic, and catheterization variables. Follow-up data included mortality, cause of death, rehospitalization, 6-month echocardiography, and functional status. Kaplan-Meier curves and log-rank tests were used to evaluate survival in subgroups. Multivariate Cox regression models were used to identify independent predictors of survival. Overall survival was 55% at 1 year, 35% at 2 years, and 23% at 3 years, with the majority of deaths (70%) classified as cardiac by an independent review committee. Rehospitalization was common (64%), although 61% of survivors at 2 years reported improved symptoms. Echocardiography at 6 months (n = 115) showed restenosis from the postprocedural valve area of 0.78 +/- 0.31 cm2 to 0.65 +/- 0.25 cm2 (P < .0001). With stepwise multivariate analysis, sequentially adding clinical, echocardiographic, and catheterization variables, the overall model identified independent predictors of survival as baseline functional status, baseline cardiac output, renal function, cachexia, female gender, left ventricular systolic function, and mitral regurgitation. Baseline and postprocedural variables were examined to identify which subgroup of patients has the best outcome after aortic valvuloplasty. A "lower-risk" subgroup (28% of the study population), defined by normal left ventricular systolic function and mild clinical functional limitation, had a 3-year survival of 36% compared with 17% in the remainder of the study group. CONCLUSIONS: Long-term survival after balloon aortic valvuloplasty is poor with 1- and 3-year survival rates of 55% and 23%, respectively. Although survivors report fewer symptoms, early restenosis and recurrent hospitalization are common.

Adult↗
PubMed1993

Percutaneous balloon pericardiotomy for the treatment of cardiac tamponade and large pericardial effusions: description of technique and report of the first 50 cases.

OBJECTIVES: This study describes the technique, clinical characteristics and results of the first 50 patients undergoing percutaneous balloon pericardiotomy as part of a multicenter registry. BACKGROUND: Percutaneous balloon pericardiotomy involves the use of a percutaneous balloon dilating catheter to create a nonsurgical pericardial window. METHODS: Patients eligible for percutaneous balloon pericardiotomy had either cardiac tamponade (n = 36) or a moderate to large pericardial effusion (n = 14). In addition to clinical follow-up, serial echocardiograms and chest X-ray films were obtained. RESULTS: The procedure was considered successful in 46 patients after a mean follow-up period of 3.6 +/- 3.3 months. Two patients required an early operation, one for bleeding from a pericardial vessel and one for persistent pericardial catheter drainage. Two patients required a late operation for recurrent tamponade. Minor complications of the procedure included fever in 6 of the first 37 patients (studied before the prophylactic use of antibiotic agents), thoracentesis or chest tube placement in 8 and a small spontaneously resolving pneumothorax in 2. Despite the short-term success of this procedure, the long-term prognosis of the 44 patients with malignant pericardial disease remained poor (mean survival time 3.3 +/- 3.1 months). CONCLUSIONS: Percutaneous balloon pericardiotomy is successful in helping to manage large pericardial effusions, particularly in patients with a malignant condition. It may become the preferred treatment to avoid a more invasive procedure for patients with pericardial effusion and a limited life expectancy.

Aged↗