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Biomedical subjects

R A Vogel

Publications and source records attributed to R A Vogel.

At least 55 records · Page 3Linked to original sources
PubMed1994

National Registry for Supported Angioplasty: results and follow-up of three years of supported and standby supported angioplasty in high-risk patients.

The National Registry of Supported Angioplasty was formed in 1988 to collect data on patients undergoing supported angioplasty. The Registry was expanded to include patients also undergoing standby supported angioplasty. In 3 years the Registry collected data on 801 patients undergoing supported or standby supported angioplasty. The data indicate that in patients with low ejection fractions and/or > or = 50% of jeopardized myocardium at risk can have an interventional procedure performed with a 6.9% risk of mortality with prophylactic or standby support, but patients with < or = 20% ejection fraction do better with prophylactic support. In addition, patients with LMCA stenosis and age > or = 70 years are at higher risk. The Registry also demonstrates good long-term results for patients who have undergone the procedure.

Adult↗
PubMed1994

Relation between coronary artery stenosis assessed by visual, caliper, and computer methods and exercise capacity in patients with single-vessel coronary artery disease. The Veterans Affairs ACME Investigators.

BACKGROUND: Practitioners often assume a close relation between angiographic coronary artery stenosis and patient functional capacity. To test this unproven hypothesis, we analyzed the relation between coronary artery stenosis measured by different methods and maximal treadmill exercise tolerance in patients with single-vessel disease before and after intervention by percutaneous transluminal coronary angioplasty (PTCA). METHODS AND RESULTS: Coronary angiography and maximal exercise testing off anti-ischemic medication were performed before random assignment of 227 patients with single-vessel coronary artery disease to PTCA or drug therapy. Six months later, angiography and exercise testing were repeated with patients assigned to PTCA off anti-ischemic therapy so that the altered coronary stenosis was the only consistent variable. Patients assigned to drug therapy were exercised on drug therapy. Coronary stenosis was assessed visually by the local investigator and quantitatively by blinded caliper and computer methods in central laboratories. Variabilities of caliper and computer measurements were established in a subset read twice. Visually estimated stenosis > or = 90% at baseline was associated with shorter exercise duration (7.9 versus 9.2 minutes, P < .04). Similar segregation at baseline was not observed with caliper or computer methods. Regardless of the method of measurement used, correlation between changes of lesion severity and exercise duration from baseline to follow-up was poor. Patients were angiographically classified as "better," "unchanged," or "worse" if follow-up stenosis was below, within, or above 2 SD of mean technical variability from baseline (+/- 18.8%, caliper, +/- 14.6%, computer). Exercise duration for PTCA patients improved among those with better lesions (+2.4 minutes, n = 50, P = .001) but also among those with unchanged lesions (+1.9 minutes, n = 41, P < or = .001). Unchanged medically treated patients improved less (+0.5 minutes, n = 86, P = .04). Results were similar when patients were angiographically classified by minimum lumen diameter. CONCLUSIONS: Handheld calipers and quantitative coronary angiography are equivalent techniques for making anatomic measurements. Neither method identified patients having reduced exercise capacity at baseline as well as visual estimation. The relation between changes of coronary stenosis and exercise duration is highly variable, at least in part because of the insensitivity of angiographic methods for detecting small but potentially important changes. Minimal anatomic improvement 6 months after PTCA does not preclude a good functional outcome. Contrary to common belief, angiographic stenosis does not correlate well with functional capacity, even in patients with single-vessel disease.

Angioplasty, Balloon, Coronary↗
PubMed1993

Prophylactic versus standby cardiopulmonary support for high risk percutaneous transluminal coronary angioplasty.

OBJECTIVES: Data from a national registry of 23 centers using cardiopulmonary support (CPS) were analyzed to compare the risks and benefits of prophylactic CPS versus standby CPS for patients undergoing high risk coronary angioplasty. BACKGROUND: Early data from the CPS registry documented a high angioplasty success rate as well as a high procedural morbidity rate. Because of this increased morbidity some high risk patients were placed on standby CPS instead of prophylactic CPS. METHODS: Patients in the prophylactic CPS group had 18F or 20F venous and arterial cannulas inserted and cardiopulmonary bypass initiated. Patients in the standby CPS group were prepared for institution of cardiopulmonary bypass, but bypass was not actually initiated unless the patient sustained irreversible hemodynamic compromise. RESULTS: There were 389 patients in the prophylactic CPS group and 180 in the standby CPS group. The groups were comparable with respect to most baseline characteristics, except that left ventricular ejection fraction was lower in the prophylactic CPS group. Thirteen of the 180 patients in the standby CPS group sustained irreversible hemodynamic compromise during the angioplasty procedure. Emergency institution of CPS was successfully initiated in 12 of these 13 patients in < 5 min. Procedural success was 88.7% for the prophylactic and 84.4% for the standby CPS group (p = NS). Major complications did not differ between groups. However, 42% of patients in the prophylactic CPS group sustained femoral access site complications or required blood transfusions, compared with only 11.7% of patients in the standby CPS group (p < 0.01). Among patients with an ejection fraction < or = 20%, procedural morbidity remained significantly higher in the prophylactic CPS group (41% vs. 9.4%, p < 0.01), but procedural mortality was higher in the standby group (4.8% vs. 18.8%, p < 0.05). CONCLUSIONS: Patients in the standby and prophylactic CPS groups had comparable success and major complication rates, but procedural morbidity was higher in the prophylactic group. When required, standby CPS established immediate hemodynamic support during most angioplasty complications. For most patients, standby CPS was preferable to prophylactic CPS during high risk coronary angioplasty. However, patients with extremely depressed left ventricular function (ejection fraction < 20%) may benefit from institution of prophylactic CPS.

Adult↗
PubMed1993

Effect of magnesium sulphate infusion on ex vivo platelet aggregation in swine.

The effect of magnesium sulphate infusion on ex vivo platelet aggregation in 11 female Yorkshire swine was observed using platelet-rich plasma and different agonists (ADP 5 mM; ADP 10 mM and collagen 1 mg/ml). Infusion of 1 g MgSO4 over 1 h produced a significant decrease in platelet aggregability. A dose-dependent effect of different ADP concentrations on platelet aggregation was noticed. Platelet inhibition was most consistent when using ADP 5 mM. We estimate this concentration of agonist as optimal in swine. The swine model is a good choice for investigation of in vivo platelet activation, especially with regard to cardiovascular research. We conclude that there is an inhibitory effect of supplemental magnesium on ex vivo platelet aggregation in swine with initial normomagnesaemia.

Adenosine Diphosphate↗
PubMed1992

Survey of practicing cardiologists in Maryland on their choice of thrombolytic therapy for acute myocardial infarction.

In November 1990, we surveyed 160 practicing community cardiologists in the state of Maryland and 20 academic cardiologists at the University of Maryland Medical Center to determine each individual's preference for aggressive versus nonaggressive therapy for various presentations of acute myocardial infarction. The survey was repeated in April 1991 following a report of the results of the Third International Study of Infarct Survival. All 100 responding cardiologists chose aggressive therapy to manage an early (less than 2 hours) acute anterior myocardial infarction in a 50-year-old patient. However, less aggressive therapy was chosen by many community cardiologists for management of early inferior acute myocardial infarction or for elderly patients. Most community cardiologists chose tissue plasminogen activator as their thrombolytic drug of choice, whereas university cardiologists favored streptokinase. Although there were substantial shifts in choice of thrombolytic agent on the repeat survey, most community physicians still chose tissue plasminogen activator over the less expensive streptokinase.

Age Factors↗
PubMed1992

Coronary angioplasty in high-risk patients with left main coronary stenosis: results from the National Registry of Elective Supported Angioplasty.

To assess the outcome of PTCA in circulatory supported patients with left main coronary artery (LMCA) stenosis, the National Registry of Elective Supported Angioplasty data bank was searched. Patients entered in the registry were considered high-risk PTCA and the PTCA was performed using percutaneous cardiopulmonary bypass (PCPB). Criteria for high risk was left ventricular ejection fraction less than or equal to 25% or a target lesion supplying greater than or equal to 50% of functioning myocardium. Of 455 patients entered in the registry, 61 (13.3%) had LMCA stenosis greater than or equal to 60%. There were 42 patients in whom the PTCA target vessel was the LMCA (PTCA-LMCA) and 19 in whom it was vessel(s) other than the LMCA (PTCA-OTHER). The mean age was similar in the 2 groups (65 +/- 10 vs. 68 +/- 9 yrs, p = ns). The left ventricular ejection fraction (LVEF) was higher in PTCA-LMCA than in PTCA-other (38 +/- 16% vs. 27 +/- 16%, p less than 0.05). The number of vessels dilated/patient was higher in PTCA-LMCA than in PTCA-OTHER (2.1 +/- 1.0 vs. 1.1 +/- 0.3, p less than 0.001). There were a total of 10 in-hospital deaths (16%) in patients with LMCA greater than or equal to 60% stenosis. This exceeds the mortality of the patients with less than 60% LMCA stenosis entered in the registry (4.5%, p less than 0.001). There were 6 in-hospital deaths (14%) in PTCA-LMCA and 4 (21%) in PTCA-OTHER (p = ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Clinical value of digital radiographic coronary quantification: comparison with visual assessment and coronary flow reserve.

The value of quantitative assessment of coronary artery dimensions at the site of the most critical coronary stenosis was assessed by comparison with the correspondent reactive hyperaemia as measured by digital subtraction angiography and with the functional results. Thirty-two coronary lesions were analysed and flow reserve data were obtained in an additional 11 vascular distributions without coronary obstruction in 19 patients. Minimal diameter less than 1.25 mm and minimal area less than 1.5 mm2 at the site of the stenosis best separated vascular distributions with inadequate hyperaemic response from those with sufficient reactive hyperaemia (chi 2 = 19.57; P less than 0.0001). Identification of lesion severity based on videodensitometric percentage area stenosis greater than 70% or percentage diameter stenosis greater than 50% yielded similar but poorer results (respectively chi 2 = 14.53; P less than 0.001 and chi 2 = 10.29; P less than 0.005). Additionally, when visually determined percentage stenosis was compared to the quantitatively assessed value, only a fair correlation was observed (r = 0.74), with visual overestimation of lesion severity by an average of 11.1 +/- 9.8% (mean +/- SD). Reactive hyperaemia in vessels with coronary obstruction could be described from minimal coronary dimensions by a quadratic equation but did not correlate closely in this patient population (r = 0.54 with minimal diameter and r = 0.58 with minimal area).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography, Digital Subtraction↗
PubMed1991

Percutaneous support devices for high risk or complicated coronary angioplasty.

Indications for coronary angioplasty have expanded to include patients with unstable acute ischemic syndromes, severe multivessel coronary artery disease and impaired left ventricular function. Several mechanical approaches have been developed as adjuncts to high risk coronary angioplasty to improve patient tolerance of coronary balloon occlusion and maintain hemodynamic stability in the event of complications. These percutaneous techniques include intraaortic balloon counterpulsation, anterograde transcatheter coronary perfusion, coronary sinus retroperfusion, cardiopulmonary bypass, Hemopump left ventricular assistance and partial left heart bypass. The intraaortic balloon pump provides hemodynamic support and ameliorates ischemia by decreasing myocardial work; it may be inserted for periprocedural complications or before angioplasty in patients with ischemia or hypotension. Anterograde distal coronary artery perfusion may be accomplished passively through an autoperfusion catheter or by active pumping of oxygenated blood or fluorocarbons through the central lumen of an angioplasty catheter. Synchronized coronary sinus retroperfusion produces pulsatile blood flow via the cardiac veins to the coronary bed distal to a stenosis. Both perfusion techniques limit development of ischemic chest pain and myocardial dysfunction in patients undergoing prolonged balloon inflations. Percutaneous cardiopulmonary bypass provides complete systemic hemodynamic support which is independent of intrinsic cardiac function or rhythm and has been employed prophylactically in very high risk patients before coronary angioplasty or emergently for abrupt closure. These and newer support devices, while associated with significant complications, may ultimately improve the safety of coronary angioplasty and allow its application to those who would otherwise not be candidates for revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1991

Impedance measurement of absolute blood flow using an angioplasty catheter: a validation study.

An angioplasty catheter was developed to allow measurement of absolute coronary blood flow during interventional procedures. This method uses electrical impedance changes induced by a 0.5 ml bolus of 5% dextrose solution and indicator-dilution principles. The indicator is injected through a port located just proximal to the dilating balloon and the resulting changes in blood impedance are measured by electrodes at the catheter tip. Excellent linear correlations were found between known flow in 2 to 4 mm to diameter plastic tubes and catheter measurements (r = 0.99) and between timed collection canine femoral artery flow and catheter measurements (r = 0.97). Final validation was performed in canine coronary arteries using electromagnetic flowmeter data as the standard (r = 0.94). Thus accurate clinical determination of absolute coronary blood flow can be accomplished using this relatively inexpensive and simple catheter technique.

Angioplasty, Balloon, Coronary↗