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Biomedical subjects

P C Block

Publications and source records attributed to P C Block.

At least 109 records · Page 6Linked to original sources
PubMed1985

Percutaneous transluminal coronary angioplasty: role in the treatment of coronary artery disease.

Percutaneous transluminal coronary angioplasty (PTCA) is indicated for many patients with symptomatic coronary atherosclerosis. It can be safely used in patients with unstable angina pectoris, multivessel coronary disease (in selected instances), multiple stenoses in single vessels, stenoses in coronary artery bypass grafts, and recent total coronary occlusion. PTCA may be useful in reestablishing coronary flow after acute myocardial infarction with coronary occlusion and in association with thrombolytic therapy for acute myocardial infarction. The primary success rate of PTCA in experienced hands should be approximately 90%. If restenosis occurs after successful PTCA, a second procedure can be used to dilate the segment with restenosis and the success rate is high. Acute coronary events are the major complications of PTCA. Less than 5% of patients need emergency coronary surgery. Mortality for PTCA is less than 1%. Complications of PTCA diminish with increasing operator experience. PTCA is not indicated for patients with long-standing complete coronary occlusions, diffuse atherosclerotic coronary stenoses without discrete stenotic segments, multiple sites of total occlusions, or "skip" areas in vessels served by bridging collaterals. Patients with main left coronary stenoses and stenoses involving both sides of large-vessel bifurcations are not considered for PTCA in most centers. The choice for or against PTCA should be made after careful assessment of the risk/benefit ratio of PTCA vs coronary bypass surgery.

Aged↗
PubMed1984

Long-term efficacy of percutaneous transluminal coronary angioplasty (PTCA): report from the National Heart, Lung, and Blood Institute PTCA Registry.

The NHLBI PTCA Registry has collected data from 3,079 patients who underwent PTCA at 105 centers from September 1977 through September 1981 that document the initial risks and benefits of PTCA. A subgroup of 2,272 patients at 65 centers was chosen to examine the long-term effects of PTCA (97% follow-up). All patients were followed for 1 year, 191 for 3 years and 57 for 4 years. Initial success occurred in 1,397 (61%), and 72% remained improved at 1 year with no further procedures; during the first year of follow-up, 14% had repeat PTCA, 12% had CABG, 3% had MI and 1.6% died. After 1 year, 67% were asymptomatic; of these, 52% had no other procedure, 7% had a second PTCA and 8% had CABG. Follow-up at 2 to 4 years was similar except that there were few repeat PTCA or CABG procedures after 1 year. The annual mortality rate after PTCA in patients with 1-vessel diseases was less than 1% per year and with multivessel CAD, 3% per year. Thus, successful PTCA alone results in sustained improvement in 84% of patients; 59% were asymptomatic (12% had repeat PTCA). PTCA offers extended effective therapy in selected patients with CAD.

Angioplasty, Balloon↗
PubMed1984

Relative cost of coronary angioplasty and bypass surgery in a one-vessel disease model.

A national study was carried out to determine the relative costs of PTCA and CABG. Baseline clinical criteria for the 2 groups were similar. Data were collected in 186 sets for the PTCA group and 175 sets for the CABG group. Male patients make up 81% of the PTCA group and 80% of the CABG group. Mean hospital stay was 12 +/- 5 days in the CABG group, compared with 4 +/- 2 days in the PTCA group (p less than 0.001). The base charges for hospital and professional components of the CABG procedure were $15,580 +/- $2,159, whereas the same charges for the PTCA procedure were $5,315 +/- $2,159 (p less than 0.001). With an 80% primary success rate, which was the group mean success rate, the average dollar savings per PTCA procedure would be $7,149, or $7,149,000 per 1,000 cases. Thus, PTCA for revascularization in 1-vessel CAD is significantly more cost-effective than CABG in the short term.

Aged↗
PubMed1984

Mechanism of transluminal angioplasty.

Experimental studies of transluminal angioplasty in atherosclerotic animal models as well as in human postmortem arteries all have shown that splitting of the atheromatous plaque occurs during angioplasty. Histologic sections of human arteries that were studied after successful angioplasty done in vivo also have shown splitting of the atheromatous plaque. The split may extend down to the internal elastic membrane. As the angioplasty balloon becomes fully inflated, the elastic media and adventitia stretch to conform to the outer diameter of the expanded balloon. Damage to medial cells may occur and may be important in keeping the artery dilated after the balloon is deflated and withdrawn. The "healing" process of the atheromatous plaque after angioplasty is poorly understood. Whether there is metabolic dissolution of atheromatous material or whether there is fibrous retraction of the atheromatous plaque against the dilated arterial wall is not known. Further studies are needed to elucidate the late changes after angioplasty.

Angioplasty, Balloon↗
PubMed1984

Surgical intervention for failed percutaneous transluminal coronary angioplasty.

From July 1978 through April 1983, 125 patients underwent attempted PTCA at the Massachusetts General Hospital. The first 25 patients were considered to be surgical candidates after failure of the PTCA attempt regardless of the presence of acute myocardial ischemia (Group I). The subsequent 100 patients (Group II) were considered to be surgical candidates only if acute myocardial ischemia was caused by a failed PTCA attempt. Four of the Group I patients (16%) required urgent operative intervention and 7 of the Group II patients (7%) required urgent operative intervention yielding, a total of 11 patients (8.8%) of the entire group. There were no hospital deaths and only 1 MI, actually documented before cardiopulmonary bypass. Women required urgent operative intervention more frequently than men (14.7% vs 6.6%). Patients with right coronary artery lesions required urgent operative intervention more often than those with left anterior descending lesions (13.0% vs 8.0%). Factors that lead to low operative mortality and myocardial infarction rates include an available operating room and team during the PTCA attempt, systemic arterial and Swan-Ganz pulmonary artery catheter pressure measurements at the time of angioplasty, intraaortic balloon pumping at the first sign of myocardial injury and expeditious surgery.

Adult↗
PubMed1984

Combined intracoronary streptokinase infusion and coronary angioplasty during acute myocardial infarction.

PTCA was performed in 28 patients with acute MI immediately after intracoronary streptokinase administration. Indications were failure to obtain reflow in 16 patients and high-grade residual stenosis in 12. PTCA was successful in 11 of 16 cases of streptokinase failure, increasing the overall reflow rate from 66% to 77%. PTCA reduced residual coronary stenosis by more than 20% in 9 of 12 cases in which streptokinase infusion was successful, with 1 acute reocclusion. The frequency of recurrent ischemic events in hospital was 76% in patients with a stenosis of 90% or greater after streptokinase infusion (no PTCA), 14% when residual stenosis was less than 90%, and 6% after successful PTCA. Late restenosis or reocclusion was documented in 5 of 11 PTCA cases (45%). Immediate PTCA after streptokinase administration produces increased clinical stability in hospital, but late restenosis is frequent.

Angioplasty, Balloon↗
PubMed1984

Effect of dextran and aspirin on platelet adherence after transluminal angioplasty of normal canine coronary arteries.

The effect of low-molecular-weight dextran and aspirin on platelet deposition after transluminal coronary angioplasty was studied in a normal canine model. Eighteen anesthetized, open-chest dogs were separated into 4 groups. All dogs received 3,000 units of intravenous heparin 10 to 20 minutes before the procedure. Dogs in Group 1 served as controls and were given no further treatment. Dogs in Group 2 received low-molecular-weight dextran by continuous intravenous infusion at a rate of 20 ml/hour for 1 hour before balloon inflation. Dogs in Group 3 were given 500 ml of low-molecular-weight dextran as an intravenous bolus over 1 hour, beginning 4 hours before the procedure. Dogs in Group 4 were fed 20 mg/kg of aspirin 3 hours before angioplasty. The dogs were killed 10 minutes after angioplasty and the arterial segments subjected to balloon inflation submitted for electron microscopic analysis. An additional group of 10 dogs was used to assess the bleeding times and platelet counts from control and drug-treated dogs. Drug treatment was associated with significant prolongation of the bleeding time and reduction in platelet number. Extensive endothelial desquamation in the area of balloon angioplasty was observed in all dogs. However, no appreciable qualitative difference in either the degree or extent of rapid platelet deposition to the exposed subendothelium was discernible between the control and any of the treatment groups. These results do not confirm previous observations with low-molecular-weight dextran. Further work on the initial and long-term platelet response after endothelial injury should be undertaken in a primate atherosclerotic model.

Angioplasty, Balloon↗
PubMed1984

Percutaneous angioplasty of stenoses of bypass grafts or of bypass graft anastomotic sites.

Forty patients who had stenoses of coronary artery bypass grafts or stenoses of the proximal or distal coronary insertion sites were treated with percutaneous transluminal angioplasty (PTA). PTA was successful in 78% of the patients. Mean stenoses were diminished from 86% to 34% in luminal diameter. One patient needed emergency coronary artery bypass grafting. There were no deaths associated with PTA. Follow-up angiography showed continued patency in asymptomatic patients, whereas in all but 1 patient with recurrent symptoms restenosis had developed at the PTA site. In 38% of patients restenosis developed after successful PTA; the highest restenosis rate was after PTA of aorta/graft anastomoses or proximal graft stenoses. In conclusion, PTA is a successful, low risk alternative to repeat coronary artery bypass grafting, although the restenosis rates at some PTA sites are high.

Adult↗
PubMed1984

A new approach to quantitation of exercise thallium-201 scintigraphy before and after an intervention: application to define the impact of coronary angioplasty on regional myocardial perfusion.

We have developed a new computer method designed to quantitate regional myocardial thallium-201 (TI-201) initial distribution, redistribution, and clearance rate. In addition, this computer method permits the generation of functional images to compare two thallium images in the same projection to one another. These functional images can be used to demonstrate the extent of redistribution and the extent of change in regional perfusion before and after an intervention. To validate and apply this new computer technique, exercise TI-201 myocardial images obtained before and 1 week after percutaneous transluminal coronary angioplasty (PTCA) were analyzed in 20 patients with isolated left anterior descending coronary artery disease. Significant improvement in initial TI-201 activity, expressed as a percentage of maximal myocardial activity, was present in the anterior (71.9 +/- 12.0 to 84.1 +/- 11.5%, p less than 0.001) and septal (66.7 +/- 15.4 to 75.2 +/- 11.0%, p less than 0.05) regions of the left ventricle 1 week after PTCA. This increase in relative anterior wall TI-201 uptake was associated with a significant reduction in the amount of TI-201 redistribution between initial and delayed postexercise images (14.7 +/- 14.6 to 3.0 +/- 13.2%, p less than 0.05) as well as an increase in TI-201 clearance rate (t 1/2 from 8.8 +/- 4.4 to 4.3 +/- 2.5 hours, p less than 0.001). Quantitative analysis of TI-201 scans demonstrated improvement in 14 of 20 patients following PTCA. Computer-derived functional difference images depicted diminution in the extent of ischemia as manifested by redistribution of TI-201.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

The results of transvenous endomyocardial biopsy can frequently be used to diagnose myocardial diseases in patients with idiopathic heart failure. Endomyocardial biopsies in 100 consecutive patients revealed a substantial incidence of myocarditis.

Transvenous endomyocardial biopsy is an accepted method to evaluate cardiac transplant rejection, but the clinical diagnostic value of the technique for other forms of cardiac disease has not been established. We performed biopsies in 100 consecutive patients without significant complications. The pathologic diagnostic information obtained was judged to be useful to the clinician in 54 and not useful in 46 patients. In 74 patients with congestive heart failure of unknown etiology and a dilated heart, useful pathologic diagnoses included myocarditis, vasculitis, doxorubicin cardiomyopathy, and congestive cardiomyopathy. In most of the patients with biopsy findings of myocarditis there were no other clinical or laboratory findings indicating the presence of this disease, and the diagnosis of myocarditis would have been overlooked without a biopsy. In 26 patients in whom there was clinical evidence of constrictive or restrictive cardiovascular physiologic characteristics, useful biopsy diagnoses included radiation-induced cardiomyopathy, endomyocardial fibrosis, amyloidosis, or no myocardial disease; in the patients without myocardial disease thoracotomies were performed for constrictive pericarditis. Transvenous endomyocardial biopsy can provide clinically useful information in the evaluation of diseases of the myocardium.

Adult↗
PubMed1984

A new method to calculate aortic valve area without left heart catheterization.

Assessment of the severity of aortic stenosis remains a commonly encountered clinical problem. Noninvasive evaluation has to date not proven sufficiently accurate in most cases to permit clinical decision making in the individual patient. Therefore, cardiac catheterization and measurement of the valve area with use of the Gorlin equation remains the standard approach in patients with suspected aortic stenosis. Doppler ultrasound allows direct measurement of blood velocity in cardiac chambers. This technique was used to study 16 patients with suspected aortic stenosis after cardiac catheterization. Aortic valve area (AVA) was calculated with the equation AVA = CO/(SEP X mean velocity), where CO is cardiac output measured by thermodilution and SEP is the systolic ejection period derived from the Doppler tracings. The resulting value was compared with valve area calculated from cardiac catheterization data and an excellent correlation was noted (r = .99). This study demonstrates that Doppler ultrasound can be used to accurately measure aortic valve area without the need for left heart catheterization.

Aged↗
PubMed1983

Percutaneous transluminal coronary angioplasty: report of complications from the National Heart, Lung, and Blood Institute PTCA Registry.

The complications reported in the first 1500 patients enrolled in the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty (PTCA) Registry are analyzed. Data were contributed from 73 centers between September 1977 and April 1981. PTCA was successful in 63% of attempts. Five hundred forty-three in-hospital complications occurred in 314 patients (21%). The most frequent complications were prolonged angina in 121, myocardial infarction (MI) in 72, and coronary occlusion in 70. One hundred thirty-eight patients (9.2%) had major complications (MI, emergency surgery or in-hospital death). One hundred two patients (6.8%) required emergency surgery, usually for coronary dissection or coronary occlusion. Sixteen patients (1.1%) died in-hospital; the mortality rate was 0.85% in patients with one-vessel disease and 1.9% in those with multivessel disease. The mortality rate was significantly higher in patients who had had bypass surgery (p less than 0.001). Nonfatal complications were significantly influenced by the presence of unstable angina (p less than 0.001) and initial lesion severity greater than 90% diameter stenosis (p less than 0.001). This report delineates and assesses the complications encountered with PTCA during its initial 3 1/2-year clinical experience. These results support the relative safety of PTCA as a method of nonsurgical myocardial revascularization in carefully selected patients.

Adult↗
PubMed1983

Coronary reocclusion after selective administration of streptokinase.

Intracoronary streptokinase was given to 40 patients with acute transmural myocardial infarction. In 34 of the patients (85%), it resulted in reflow or improved flow. Six patients showed no reflow and six reocclusion within 2 hours. No consistent explanation was found for this resistance to therapy. Five other patients developed reocclusion after 6 days to 11 months, when heparin or warfarin anticoagulation had been stopped. Percutaneous angioplasty at the time of streptokinase infusion was performed in seven, with six successes. Bypass surgery was performed after successful streptokinase administration in eight. Follow-up revealed recurrent ischemia in patients successfully treated with streptokinase alone, but not in patients with successful angioplasty or bypass surgery. Long-term coronary patency after thrombolysis may require careful anticoagulation or a procedure that modifies or bypasses the residual stenosis.

Angioplasty, Balloon↗
PubMed1982

Percutaneous transluminal coronary angioplasty: report from the Registry of the National Heart, Lung, and Blood Institute.

Data have been collected from 34 centers in the United States and Europe performing percutaneous transluminal coronary angioplasty since September 1977. The procedure was carried out in 631 patients, with an average age of 51 years (range 23 to 76), of whom 80 percent had single vessel coronary disease, 17 percent had double or triple vessel disease and 3 percent had stenosis of the left main coronary artery. Coronary angioplasty was successful (greater than 20 percent decrease of coronary stenosis) in 59 percent of the stenosed arteries. The mean degree of stenosis was reduced from 83 to 31 percent. Emergency coronary bypass operation was required in 40 patients (6 percent). Myocardial infarction occurred in 29 patients (4 percent). In-hospital death occurred in six patients (1 percent), three with single vessel and three with multivessel disease. Ninety-one patients have been followed up for at least 1 year after coronary angioplasty. Of the 65 patients with an initially successful angioplasty, 83 percent were in improved condition compared with their status before angioplasty. Thus, the initial satisfactory results obtained in a few centers have now been confirmed in many centers using transluminal coronary angioplasty.

Adult↗
PubMed1982

The association of clinical, psychosocial, and angiographic variables with work status in patients with coronary artery disease.

The bearing of clinical history, epidemiological risk factors, psychosocial factors, angiographic findings, and treatment characteristics was studied in relationship to the work status of 182 men who underwent coronary angiography because of presumptive coronary artery disease. Follow-up at one year found 42% of the cohort persistently unemployed or working at a lower level, 40% at the same job, and 19% at a more demanding job. Multiple regression analysis was used to derive the most important variables predictive of work status. Neither number of vessels diseased nor Coronary Artery Bypass Graft surgery entered the multiple regression analysis. Instead, the most important variables, listed in decreasing order of importance, are: age, subsequent cardiac morbid events, past myocardial infarction, and mood during the follow-up year. Together, they account for 24% of the variance in work status outcome (p less than 0.001).

Angina Pectoris↗
PubMed1982

Improved results of surgical management of postinfarction ventricular septal rupture.

Fifty-five patients had surgical repair of postinfarction ventricular septal rupture in Massachusetts General Hospital from 1968 through 1981. In patients operated more than three weeks after infarction, hospital survival has been 93% (14/15). Before 1975 in patients operated less than three weeks after infarction, hospital survival was 41% (7/17). In this same era patents operated for septal rupture with cardiogenic shock present before operation had a hospital survival rate of only 27% (3/11). Before 1975 patients with cardiogenic shock were supported with intra-aortic balloon pumping (IABP) and vasopressors, and operation deferred pending hemodynamic stabilization. Before 1975 patients with anterior septal rupture had a hospital survival rate of 64% (9/14), while patients with posterior septal rupture had a hospital survival rate of only 38% (5/13). This difference in survival according to the location of septal rupture occurred despite comparable numbers of patients in each group requiring early operation, as well as incidence of cardiogenic shock. Since January 1, 1975 patients operated less than three weeks after infarction have had an overall hospital survival rate of 70% (16/23). Of the 10 most recent patients operated early, nine are survivors. In patients with anterior defects 85% (11/13) survived, while in patients with posterior defects 67% survived (10/15). In patients operated with cardiogenic shock present before operation, survival has been 67% (10/15). Changes in management leading to improved results include (1) immediate operation for patients with cardiogenic shock, (2) cold cardioplegic protection of the myocardium, and (3) prosthetic replacement of posterior left ventricular free wall defect, after infarctectomy and septal repair, in patients with posterior septal rupture.

Adult↗