A new bioabsorbable intravascular stent: in vitro assessment of hemodynamic and morphometric characteristics

Currently available intracoronary stents are permanent and their placement may be complicated by thrombosis and restenosis. We have developed a new bioresorbable stent constructed of type I collagen. This stent has a compliant tubular structure that is self expanding and carries a net negative surface charge to increase hemocompatibility. In vitro histologic and morphometric examination was performed by deploying the stent in six pressure fixed explanted porcine arteries. Morphometry revealed a close relationship between the stent external diameter 2.9 +/- 0.4 mm) and the arterial lumen diameter (3.0 +/- 0.4 mm). A relative reduction in arterial lumen diameter secondary to stent placement of 17% to 26% was observed. Folding of the stent wall was noted in those preparations where the stent external diameter was larger than the arterial lumen diameter. Polyvinyl chloride (PVC) tubing was used as a mock arterial segment for flow studies. Flow at baseline and following stent placement was determined at perfusion pressures of 10, 50, and 80 mmHg. A modest reduction in flow following stent placement of between 2% and 6% was observed. Thus, type I collagen may be used to construct a self expanding tubular stent. Morphometric and hemodynamic evaluation reveals a modest impact on arterial lumen dimensions and flow.

The occurrence of early sudden coronary artery occlusion following angioplasty may be predicted from the clinical characteristics of the patients and their coronary lesion morphology

The aim of this study was to assess whether the incidence of early occlusion following angioplasty was greater among patients with unstable angina and whether the coronary lesions prone to early occlusion could be predicted from their angiographic appearance. Seventy-seven patients who had had a first angioplasty of a native vessel for stable or unstable angina in one twelve month period were included. The angiographic appearances of the angioplastied lesions were classified as either Type 1, which were smooth and unlikely to have thrombus or intimal rupture, or Type 2, which were irregular due to thrombus or intimal rupture. The lesion classification was compared to the patients' clinical features, i.e. stable or unstable angina, and the outcome of the angioplasty. Type 2 lesions occurred in 25% of patients with stable angina but 49% of patients with unstable angina (p less than 0.05). Early sudden occlusion of the angioplastied vessel occurred in 24% of patients with unstable angina but in only 3% of patients with stable angina (p less than 0.05) and in 6% of Type 1 lesions compared with 24% of Type 2 lesions (p less than 0.05). Thus it is possible to identify the clinical characteristics and angiographic appearances of those patients undergoing angioplasty who are most likely to experience early vessel occlusion.

Coronary thrombosis postpartum in a young woman with Still's disease

A young woman with Still's disease sustained a small myocardial infarction 12 weeks after the delivery of a healthy male infant. This pregnancy was complicated by late onset proteinuric hypertension. Coronary angiography nine days after infarction revealed intracoronary thrombus which had resolved by 3 months with antithrombotic therapy. The angiographic appearances at 3 months suggested that a local vasculitis may have been the precipitating cause.

One-year results of the Thrombolysis in Myocardial Infarction investigation (TIMI) Phase II Trial

BACKGROUND

The Thrombolysis in Myocardial Infarction (TIMI) Phase II Trial randomized 3,339 patients to either an invasive (INV, n = 1,681) or a conservative (CON, n = 1,658) strategy after intravenous recombinant tissue-type plasminogen activator (rt-PA) for acute myocardial infarction.

METHODS AND RESULTS

The patients assigned to the INV strategy routinely underwent cardiac catheterization, and when anatomically appropriate, percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting 18-48 hours after infarction. CON patients had these procedures only in response to the occurrence of spontaneous or provoked ischemia. One-year follow-up data are available in 3,316 patients (99.3%). The primary trial end point, death and nonfatal reinfarction, occurred in 14.7% of INV patients and in 15.2% of CON patients (p = NS). When analyzed individually, there was no difference (p = NS) in death (INV, 6.9%; CON, 7.4%) or recurrent infarction (INV, 9.4%; CON, 9.8%) between the two groups. Anginal status at 1 year was also similar. Cardiac catheterization and PTCA were performed more often in INV (98.0% and 61.2%, respectively) compared with CON (45.2% and 20.5%, respectively) patients. At 1 year, the cumulative number of patients who underwent coronary bypass surgery (INV, 17.5%; CON, 17.3%) was similar in the two groups.

CONCLUSIONS

The INV and CON strategies resulted in similar favorable outcomes at 1 year of follow-up. In particular, the rates of mortality and reinfarction were not different and were impressively low in both groups. One possible advantage of the INV strategy was detected in subgroup analyses. In patients with a history of myocardial infarction, the data are suggestive that 1-year mortality was lower in INV patients (10.3%) than in CON patients (17.0%) (p = 0.03).

Disuse inhibition of newly functional coronary collateral circulation in ponies

We evaluated the loss of coronary collateral function in the absence of stimulation (disuse inhibition) by doubling the interval between successive left anterior descending coronary artery (LAD) occlusions in ponies in which collateral function initially had been enhanced by 2-min occlusions at 30-min intervals. Before collateralization, occlusion caused segment systolic shortening, velocity of shortening, and stroke work index in the LAD-dependent left ventricular apex to decrease, whereas heart rate and left ventricular end-diastolic pressure increased. After 476 +/- 102 occlusions, segment function recovered to preocclusion levels and hemodynamics were unchanged during occlusion. Occlusion did not elicit sustained functional deterioration until the occlusion interval was greater than or equal to 32 h. During the occlusion after the 128-h interval, segment systolic shortening, velocity of shortening, and stroke work index were reduced 69 +/- 8, 38 +/- 9, and 46 +/- 13%, respectively. Percent recovery of systolic shortening during successive occlusions declined exponentially (T1/e = 102.0 +/- 17.3 h). Thus, in ponies collateral function progressively declines when the occlusion interval is greater than or equal to 32 h, but complete inhibition does not occur even after 128 h without occlusion. This indicates that collateral function in ponies can be maintained by occlusions that are far less frequent than those needed for initial collateral development. The long time constant of collateral disuse inhibition suggests that equine collaterals are quite resistant to the effects of occlusion cessation and differ from canine collaterals in that respect.

Coronary angioplasty performed within the thrombolysis in Myocardial Infarction II study

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) of the infarct-related artery was performed within 42 days of recombinant tissue-type plasminogen activator (rt-PA) administration in 1,414 of the 3,534 patients who participated in the Thrombolysis In Myocardial Infarction (TIMI) II study. Primary angiographic success was obtained in 88.7%, with bypass surgery within 24 hours in 3.3% and death within 24 hours in 0.7% of patients. By 1 year, 25.1% of the 1,414 patients had sustained one or more adverse outcomes including death (3.6%), reinfarction (8.4%), or the need for further revascularization (20%).

METHODS AND RESULTS

Despite these generally favorable results, multivariate testing identified several anatomic and clinical subgroups as having an increased risk ratio (RR) for adverse outcome: Unsuccessful PTCA was more common in patients undergoing protocol-assigned PTCA within 2 hours of rt-PA administration (RR, 2.7; p less than 0.001) and in patients over age 70 years (RR, 1.7; p = 0.034). The need for further revascularization within 1 year was increased in the 30.4% of patients with multivessel disease (RR, 2.5; p less than 0.001), patients with prior angina (RR, 1.4; p less than 0.006), or those undergoing ischemia-driven PTCA within 15 hours of rt-PA administration (RR, 1.7; p = 0.022). The risk of death or recurrent infarction within 1 year was increased by the presence of multivessel disease (RR, 1.6; p = 0.007) or prior angina (RR, 1.5; p = 0.014).

CONCLUSIONS

These observations do not necessarily apply to patients undergoing primary PTCA (or PTCA after other thrombolytic agents); however, they do offer a unique yardstick against which to evaluate the results of PTCA in myocardial infarction.

Safety and efficacy of a new regimen of intravenous recombinant tissue-type plasminogen activator potentially suitable for either prehospital or in-hospital administration

The safety and efficacy of a new regimen of intravenous recombinant tissue-type plasminogen activator (rt-PA) potentially suitable for either pre- or in-hospital administration were assessed in 60 patients with acute myocardial infarction in an open label coronary angiographic study. The regimen consisted of a 20-mg bolus dose followed 30 min later by a delayed infusion of 80 mg over 2 h. This regimen was designed to facilitate prehospital administration of rt-PA. Infarct-related artery patency (Thrombolysis in Myocardial Infarction [TIMI] grade 2 or 3 flow) was observed in 40 of 53 patients at 60 min (75.5%, 95% confidence intervals [CI] 61% to 84%) and in 55 of 60 patients at 90 min (91.7%, 95% CI 80% to 95%) after the rt-PA bolus. By 90 min the majority of patients (55%) exhibited TIMI grade 3 flow; infarct artery patency at 120 min was 84.9%. During hospitalization definite recurrent ischemia occurred in nine patients (15%); nonfatal recurrent infarction was noted in one (1.7%). Four patients (6.7%) experienced major bleeding, including one with intracranial bleeding. There were seven deaths (11.7%). Mortality was significantly influenced by the occurrence of cardiogenic shock, which was present in five patients at the time of enrollment. Blood fibrinogen levels were obtained before and during rt-PA infusion. At baseline and 30 and 150 min after the bolus dose, the mean fibrinogen level (+/- SD) was 284.83 +/- 77.39, 237.96 +/- 76.92 and 192.04 +/- 57.82 mg/dl, respectively. Compared with the baseline value, there was a significant (p less than 0.05) decrease in fibrinogen at both 30 and 150 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective versus routine predischarge coronary arteriography after therapy with recombinant tissue-type plasminogen activator, heparin and aspirin for acute myocardial infarction. TIMI II Investigators

To ascertain whether predischarge arteriography is beneficial in patients with acute myocardial infarction treated with recombinant tissue-type plasminogen activator (rt-PA), heparin and aspirin, the outcome of 197 patients in the Thrombolysis in Myocardial Infarction (TIMI) IIA study assigned to conservative management and routine predischarge coronary arteriography (routine catheterization group) was compared with the outcome of 1,461 patients from the TIMI IIB study assigned to conservative management without routine coronary arteriography unless ischemia recurred spontaneously or on predischarge exercise testing (selective catheterization group). The two groups were similar with regard to important baseline variables. During the initial hospital stay, coronary arteriography was performed in 93.9% of the routine catheterization group and 34.7% of the selective catheterization group (p less than 0.001), but the frequency of coronary revascularization (angioplasty or coronary artery bypass surgery) was similar in the two groups (24.4% versus 20.7%, p = NS). Coronary arteriograms showed a predominance of zero or one vessel disease (stenosis greater than or equal to 60%) in both groups (routine catheterization group 73.1%, selective catheterization group 61.3%). During the 1st year after infarction, rehospitalization for cardiac reasons and the interim performance of coronary arteriography were more common in the selective catheterization group (37.9% versus 27.6%, p = 0.007 and 28.6% versus 11.6%, p less than 0.001, respectively); however, the interim rates of death, nonfatal reinfarction and performance of coronary revascularization procedures were similar. At the end of 1 year, coronary arteriography had been performed one or more times in 98.9% of the routine catheterization group and 59.4% of the selective catheterization group (p less than 0.001), whereas death and nonfatal reinfarction had occurred in 10.2% versus 7.0% (p = 0.10) and 8.6% versus 9.0% (p = 0.87), respectively. Because the selective coronary arteriography policy exposes about 40% fewer patients to the small but finite risks and inconvenience of the procedure without compromising the 1 year survival or reinfarction rates, it seems to be an appropriate management strategy.

Myocardial blood flow, metabolism, and function with repeated brief coronary occlusions in conscious ponies

Studies were performed in the conscious pony instrumented with a Doppler flow probe and hydraulic occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium and anterior interventricular vein. Two-minute LAD occlusions were performed every 30 min continuously or during working hours. Data on release of catabolites (potassium, hydrogen ions, and lactate) and norepinephrine from the initially dysfunctional region were obtained periodically during a regimen of 445 +/- 56 occlusions in six animals. Regional myocardial blood flow was measured (microsphere method) before and after an occlusion regimen in four animals. Marked release of catabolites and norepinephrine from the initially dysfunctional region was noted in association with early occlusions when myocardial segment function was severely reduced. With further occlusions, release of these substances decreased while segment function improved. Blood flow was markedly decreased in the initially dysfunctional region during an early occlusion but was at the control level during a later occlusion. Although the metabolic findings are consistent with protection due to "ischemic preconditioning" and no increase in collateral perfusion, the inverse relationship noted between catabolite release and segment function is best explained by flow-dependent mechanisms. These results, together with the myocardial blood flow data, serve to validate a previous assumption that protection against regional myocardial dysfunction under these conditions is due to increased collateral perfusion.

Time delays in the diagnosis and treatment of acute myocardial infarction: a tale of eight cities. Report from the Pre-hospital Study Group and the Cincinnati Heart Project

To establish the magnitude of prehospital and hospital delays in initiating thrombolytic therapy for acute myocardial infarction, the time from telephone 911 emergency medical system (EMS) activation to treatment and its components were analyzed from eight separate ongoing trials. This included estimates of ambulance response time, prehospital evaluation and treatment time, and time from admission to the hospital to initiation of thrombolytic therapy. The average time from EMS activation to patient arrival at the hospital was prospectively determined to be 46.1 +/- 8.2 minutes in 3715 patients from eight centers. The time from admission to the hospital to initiation of thrombolytic therapy was retrospectively determined to be 83.8 +/- 55.0 minutes in a separate group of 730 patients from six centers. Both the prehospital and hospital time delays were much longer than those perceived by paramedics and emergency department directors. Shorter hospital time delays were observed in patients in whom a prehospital ECG was obtained as part of a protocol-driven prehospital diagnostic strategy and a diagnosis of acute infarction made before arrival at the hospital (36.3 +/- 11.3 minutes in 13 patients). These results show that the magnitude of time required to evaluate, transport, and initiate thrombolytic therapy will preclude initiation of treatment to most patients within the first hour of symptoms. Implementation of a protocol-driven prehospital diagnostic strategy may be associated with a reduction in time to thrombolytic therapy.

Intravenous recombinant tissue-type plasminogen activator in patients with unstable angina pectoris. Results of a placebo-controlled, randomized trial

Because thrombus formation may contribute to coronary obstruction in patients with unstable angina pectoris, we performed a pilot investigation to determine whether thrombolytic therapy can relieve coronary narrowing in this acute ischemic syndrome. Sixty-seven patients with rest angina and angiographic evidence of coronary stenosis were randomly assigned to receive either low-dose intravenous recombinant tissue-type plasminogen activator (rt-PA) (0.75 mg/kg over 1 hour), high-dose intravenous rt-PA (0.75 mg/kg over 1 hour; total dose, 100 mg over 6 hours), or intravenous placebo followed by repeat coronary angiography at 24-48 hours to assess change in the severity of coronary narrowing. Each patient also received oral aspirin and intravenous heparin. Mean values of coronary stenosis severity (percent of diameter reduction) declined to a similar extent in each group: placebo, 75 +/- 14% to 72 +/- 14% (p = 0.07); low-dose rt-PA, 75 +/- 16% to 71 +/- 18% (p = 0.03), and high-dose rt-PA, 82 +/- 11% to 77 +/- 17% (p = 0.18), with only the low-dose rt-PA group achieving statistical significance. Resolution of intracoronary filling defects, increase in antegrade flow grade, or both also occurred equally among the three groups. There was considerable variation in individual patient response. Between 29% and 50% of patients within each group demonstrated a decrease in stenosis severity, whereas 50% to 57% noted either improvement in antegrade flow or resolution of intracoronary thrombus. There was no difference in incidence of major bleeding events among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of immediate invasive, delayed invasive, and conservative strategies after tissue-type plasminogen activator. Results of the Thrombolysis in Myocardial Infarction (TIMI) Phase II-A trial

To assess the value and timing of percutaneous transluminal coronary angioplasty (PTCA) after thrombolytic therapy for acute myocardial infarction (AMI), 586 patients in the Thrombolysis in Myocardial Infarction Study Phase II-A were randomized among three treatment strategies, one using immediate coronary arteriography followed by PTCA if appropriate (immediate invasive strategy group, n = 195), a second that deferred angiography and PTCA for 18-48 hours (delayed invasive strategy group, n = 194), and a third, more conservative, approach in which PTCA was used only if ischemia occurred spontaneously or at the time of predischarge exercise testing (conservative strategy group, n = 197). Predischarge contrast left ventricular ejection fraction, the primary study end point, was similar among the patients in all three treatment groups and averaged 49.3%. The finding of a patent infarct-related artery at the time of predischarge arteriography was equally common among the patients in the three groups (mean, 83.7%); however, the mean residual infarct artery stenosis was greater in the patients in the conservative strategy group (67.2%) as compared with the patients in the immediate invasive (50.6%) and the delayed invasive strategy groups (47.8%) (p less than 0.001). Immediate invasive strategy led to a higher rate of coronary artery bypass graft surgery (CABG) after PTCA (7.7%) than did delayed invasive and conservative strategies (2.1% and 2.5%, respectively; p less than 0.01). Furthermore, among patients not undergoing CABG during the first 21 days, blood transfusion of more than 1 unit was used in 13.8% of the patients in the immediate invasive strategy group, 3.1% of the patients in the delayed invasive strategy group, and 2.0% of the patients in the conservative strategy group (p less than 0.001). At 1-year follow-up, the three treatment groups had similar cumulative rates of mortality (8.7%, pooled over all groups), fatal and nonfatal reinfarction (8.5%), combined death and reinfarction (14.5%), and CABG (17.2%), although the cumulative performance rate of PTCA remained higher in the invasive groups (immediate invasive strategy group, 75.8%; delayed invasive strategy group, 64.3%; and conservative strategy group, 23.9%; p less than 0.001). Thus, because conservative strategy achieves equally good short- and long-term outcome with less morbidity and a lower use of PTCA, it seems to be the preferred initial management strategy.

The Thrombolysis in Myocardial Infarction (TIMI) Trial phase II: additional information and perspectives

Given the many thrombolytic agents and the number of ways in which they can be combined with mechanical revascularization, the treatment of acute myocardial infarction has been the subject of active study and lively debate, which are likely to continue for some time. Several studies, including TIMI IIA (2,3,10,22), have suggested that immediate catheterization and angioplasty offer no clinical benefit and have a greater complication rate than a more delayed invasive strategy, but TIMI II (1) and SWIFT (16) trials have suggested that an even more conservative strategy of reserving catheterization and coronary angioplasty after thrombolytic therapy for patients with recurrent spontaneous or exercise-induced ischemia may be the most desirable approach for the majority of patients similar to those entered into these trials.

Systolic coronary occlusion due to myocardial bridging--a rare cause of ischaemia

Myocardial bridging causing systolic occlusion of the left anterior descending coronary artery was identified in a 47-year-old man with angina. A fixed anterolateral wall defect was demonstrated on thallium imaging and he underwent successful division of the bridge resulting in abolition of his symptoms and disappearance of the thallium defect.

Pacemaker-induced superior vena cava syndrome: report of four cases and review of the literature

Superior vena cava syndrome due to transvenous pacing leads is a rare event. We describe four cases. One occurred among 3,100 primary pacemaker insertions performed at our institution. In the other three cases the primary insertion had been performed elsewhere. Over 30 cases have been reported previously. Local infection, which preceded the development of superior vena cava syndrome in each of our four cases, and the presence of a severed retained lead, as in three of our cases, are important predisposing factors. There is no strong evidence that multiple lead insertion, if each lead remains intact, significantly increases the risk. The pathology at the site of obstruction includes thrombosis and in some cases fibrotic narrowing. Venous angiography is useful to show the site of obstruction, the extent of collateral circulation and to assess the response to treatment. Treatment should include removal of any infected pacemaker apparatus, anticoagulation and, if symptoms are of recent onset, thrombolytic therapy. Most patients improve but in those who do not angioplasty or surgical relief of the obstruction may be helpful.

Controlled release salbutamol tablets versus aminophylline in the control of reversible airways obstruction

A crossover study was carried out to compare the acceptability and efficacy of 8 mg twice daily controlled release salbutamol with 525 or 700 mg twice daily aminophylline in patients with reversible obstructive airways disease. Patients were randomly allocated into two groups to determine the treatment order. A 2-week run-in period was used to titrate the aminophylline dosage, followed by a crossover phase of two 4-week treatments. A total of 68 patients, aged 20-75 years, entered the study and 39 (57%) completed it. The two drugs differed in the pattern and severity of their side-effects. Of the 15 patients withdrawn because of severe adverse events, 12 were unable to tolerate treatment with aminophylline. There were no statistically significant differences between the treatments for lung function tests measured at the clinic, peak expiratory flow rate recorded by the patients, frequency (or severity) of asthma symptoms or the use of relief medication. Patients completing the study expressed a preference for controlled release salbutamol in 17/25 (68%) cases.

Oestrone sulphate measurement in bovine serum during late pregnancy and its relationship with the number of calves born

A radioimmunoassay developed for the measurement of oestrone sulphate in bovine serum was used to determine levels of hormone in cows. The cows were sampled as part of an embryo transfer programme designed to investigate the production of twin calves. The concentration of oestrone sulphate in serum was higher in cows carrying twin calves, but the difference did not become significant until around 220 days' gestation. The predictive value of the test could be used as a guide to increase feeding of cows pregnant with more than one calf.

Comparison of complications during percutaneous transluminal coronary angioplasty from 1977 to 1981 and from 1985 to 1986: the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry

Because the effects of changing technology in percutaneous transluminal coronary angioplasty, increased operator experience and use of the procedure in patients with extensive disease are unknown in regard to complication patterns, the initial 1977-1981 cohort and the recent 1985-1986 cohort of the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry were analyzed with respect to complications. Compared with the initial cohort of 1,155 patients, the 1,801 new cohort patients were older and had an increased prevalence of multivessel coronary artery disease, depressed left ventricular function and prior infarction. Overall complication rates in the recent cohort were either unchanged or decreased from the rates in the initial cohort despite a higher risk patient population. The most significant decreases were in the incidence of coronary spasm (p less than 0.001) and the need for emergency coronary bypass surgery (p less than 0.01). Overall in-hospital mortality was low but was dependent on the extent of vessel disease--0.2% for single vessel disease, 0.9% for double vessel disease and 2.2% for triple vessel disease (p less than 0.001 for linear trend). Acute coronary complications of branch occlusion, dissection or abrupt closure were associated with increased rates of death, nonfatal infarction or need for emergency surgery. Factors showing a multivariate association with increased mortality included a history of congestive heart failure (p less than 0.001), age greater than or equal to 65 years (p less than 0.01), triple vessel or left main coronary artery disease (p less than 0.05), female gender (p less than 0.05) and new onset angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of a new angioplasty catheter for severely narrowed coronary lesions

Conventional over the wire dilation catheters may be unsuccessful in crossing coronary lesions that are severely narrowed. Hence, a new, extremely low profile coronary angioplasty catheter specifically designed to dilate such lesions was investigated. The catheter features a 2.0, 2.5 or 3.0 mm (inflated diameter) balloon mounted on a guide wire. The deflated profile of the 2.0 mm balloon measures 0.020 +/- 0.001 in. (0.51 +/- 0.03 mm). The catheter can be used in conjunction with 7F angiographic or 8F guide catheters. The catheter was used in 61 patients, aged 43 to 86 years, with predominantly Canadian Cardiovascular Society class III-IV angina. Dilation was attempted in 77 lesions. Lesion length averaged 5.7 +/- 3.1 mm (mean +/- 1 SD), minimal diameter 0.51 +/- 0.25 mm and internal vessel diameter 2.27 +/- 0.43 mm. Sixty lesions (78%) were successfully dilated to less than 50% residual stenosis with this catheter alone; nine lesions were further dilated with a larger balloon catheter. The new catheter was unable to cross 13 lesions (17%); only 2 of these lesions were subsequently crossed with a conventional over the wire system. On the other hand, the catheter was used after failure of conventional dilating catheters in 21 lesions and was successful in 16. The new catheter was particularly valuable for distal lesions and those demonstrating 90 to 99% diameter reduction. For all lesions crossed, stenosis decreased from 76 +/- 11 to 29 +/- 12% after 2.9 +/- 2.7 inflations and peak inflation pressure of 8.0 +/- 2.9 bar. Complications were rare; coronary occlusion occurred in two lesions (3%) and dissection in three lesions (4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Objective assessment of coronary angioplasty for multivessel disease: results of exercise stress testing

The efficacy of coronary angioplasty in multivessel coronary artery disease was evaluated in a series of 145 consecutive patients in whom angioplasty had been successful and in whom a follow-up exercise stress test was performed within 2 months. Exercise stress test results of these patients with multivessel disease were compared with those of 177 patients with single vessel disease after successful coronary angioplasty. The postangioplasty exercise test showed ischemia in 13% of patients with single vessel and 29% of those with multivessel disease, although only 7 and 13%, respectively, experienced angina. The mean exercise duration was comparable for patients with multivessel disease (453 +/- 174 s) and single vessel disease (476 +/- 166 s). To assess the impact of the degree of revascularization in patients with multivessel disease on the results of exercise testing, 48 patients with completely revascularized vessels and 97 with incompletely revascularized vessels were evaluated. The mean exercise duration (459 +/- 178 versus 450 +/- 173 s), mean maximal heart rate (132 +/- 31 versus 136 +/- 25 beats/min) and mean systolic blood pressure (174 +/- 25 versus 170 +/- 26 mm Hg) were similar in completely and incompletely revascularized groups. Exercise-induced angina occurred in 13% of both groups. Ischemic ST segments were more common in the incompletely revascularized group (34 versus 19%, p = 0.06). Thus, exercise stress testing provides evidence that successful angioplasty can relieve electrocardiographic manifestations of ischemia as well as anginal symptoms in the majority of patients with either single or multivessel coronary artery disease who are suitable candidates for the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous double balloon coronary angioplasty through a single guiding catheter for bifurcation lesions

To enhance the safety, efficacy and expediency of coronary bifurcation lesion angioplasty, we report the use of two dilatation catheters, advanced simultaneously through a single guide catheter in three patients. Successful dilatation was performed in each. The technique involves the use of either two new low-profile dilatation catheters in an 8 French large lumen guide catheter or a single new low-profile dilatation catheter coupled with a conventional over-the-wire catheter within a new large lumen 9 French guide.

Coronary angioplasty for patients with multivessel coronary artery disease: follow-up clinical status

To determine the value of percutaneous transluminal coronary angioplasty (PTCA) for patients with multivessel coronary artery disease, we reviewed follow-up data of 92 consecutive multivessel disease patients in whom PCTA had been successful and in whom at least 6 months had elapsed. Clinical outcome of multivessel disease patients was compared to that of 189 patients with single-vessel disease who experienced successful PTCA. Eighty percent of multivessel disease patients noted clinical improvement at follow-up. More single-vessel disease patients, however, were free of angina (77% vs 63%, p = 0.02), were not taking long-acting antianginal medicationS (46% vs 27%, p less than 0.001), and had repeat PTCA less often (5% vs 12%, p = 0.05) than multivessel disease patients. The incidence of late clinical events such as myocardial infarction, coronary artery bypass surgery, and death was low in both single- and multivessel disease patients. To determine whether the degree of revascularization achieved accounted for differences between single- and multivessel disease outcome, PTCA for multivessel disease was classified as either complete or incomplete revascularization. Those patients classified as having incomplete revascularization, although they had multivessel coronary artery disease, had only one significant ischemic zone and this was successfully revascularized by PTCA. There was no significant difference in anginal status or incidence of myocardial infarction, coronary artery bypass surgery, or death between the two multivessel disease subgroups. Thus, PTCA is of clinical value for selected patients with multivessel coronary artery disease, even in those who are incompletely revascularized by design.

Coronary angioplasty after recombinant tissue-type plasminogen activator in acute myocardial infarction: a report from the Thrombolysis in Myocardial Infarction (TIMI) Trial

To assess the utility of percutaneous transluminal coronary angioplasty after successful thrombolytic therapy for patients with acute myocardial infarction, the outcome of 201 patients who received intravenous recombinant tissue-type plasminogen activator (rt-PA) was analyzed. Reperfusion of the infarct-related artery was observed in 132 patients who were assessed for potential coronary angioplasty at 18 to 48 hours after treatment. Coronary angioplasty was performed in 52 patients (39%). Reasons for not performing angioplasty included unsuitable coronary anatomy, presence of residual stenosis of less than 60% and the need to perform an earlier procedure. When attempted, coronary angioplasty was successful in 96% of patients and was associated with a decrease in coronary stenosis from 85 to 30%. No patient experienced a major complication associated with coronary angioplasty. Of 36 patients undergoing predischarge coronary angiography after successful angioplasty, the infarct-related artery remained patent in 97.2%. Thus, coronary angioplasty is feasible and safe in patients who achieve coronary reperfusion after intravenous rt-PA for acute myocardial infarction. Not all patients who achieve reperfusion, however, are suitable for coronary angioplasty. When attempted, angioplasty is usually successful and associated with sustained patency of the infarct-related artery.

Angiographic findings when chest pain recurs after successful percutaneous transluminal coronary angioplasty

Angiographic and clinical characteristics of 102 consecutive patients who underwent coronary cineangiography for assessment of recurrent angina pectoris after successful percutaneous transluminal coronary angioplasty (PTCA) were reviewed. Based on angiographic findings, patients were classified as having restenosis (n = 63), development of new, significant coronary stenosis (n = 15), incomplete revascularization (n = 9) or no significant coronary artery disease (n = 15). Eighteen clinical and technical characteristics of the study group were analyzed as predictors of angiographic outcome. The groups did not differ in terms of age, gender, number of inflations performed, peak inflation pressure or in the pre- or post-PTCA stenosis or gradient. The time from PTCA to onset of recurrent angina was the most powerful predictor of angiographic outcome. Patients in whom symptoms developed within 1 month of PTCA usually had incomplete revascularization or no coronary narrowing. Restenosis was the most common explanation for chest pain 1 to 6 months after PTCA. Angina recurring more than 6 months after PTCA was usually due to development of new, significant coronary artery narrowings.

Superiority of intracoronary papaverine to radiographic contrast for measuring coronary flow reserve in patients with ischemic heart disease

Measurement of coronary flow reserve has been suggested as an adjunct to anatomic assessment of coronary stenoses in patients with ischemic heart disease. We compared papaverine hydrochloride and radiographic contrast to determine which agent was superior for the determination of coronary flow reserve. Coronary flow reserve was determined during cardiac catheterization by means of digital coronary angiography and parametric imaging. Two groups of patients were studied. Among patients in group 1, coronary flow reserve was determined by means of both papaverine and contrast. In group 1 patients with normal coronary arteries, papaverine-induced flow reserve was greater than contrast-induced reserve in all but one vascular region (n = 9, 4.98 +/- 1.15 vs 3.56 +/- 0.89; p = 0.29). Group 1 patients with coronary disease also demonstrated significantly greater flow reserve with papaverine (n = 25, 2.57 +/- 0.20 vs 1.83 +/- 0.11, p less than 0.01). Group 2 included patients with single-vessel coronary artery stenoses. These patients were studied by means of either papaverine or contrast to determine coronary flow reserve for both the stenotic "ischemic" region and an adjacent nonstenotic, "nonischemic" region. Those patients in group 2 who were studied by means of contrast had a modest difference between flow reserve values in the nonischemic and those in the ischemic regions (n = 15, 1.78 +/- 0.10 vs 1.26 +/- 0.09; p less than .0001) with considerable overlap. Patients studied by means of papaverine had a much greater separation in flow reserve between nonischemic and ischemic regions (n = 22, 2.78 +/- 0.19 vs 1.46 +/- 0.14; p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of coronary flow reserve using digital angiography before and after successful percutaneous transluminal coronary angioplasty

Important alterations of coronary blood flow and coronary flow reserve occur during percutaneous transluminal coronary angioplasty (PTCA). This study evaluated these alterations using digital subtraction angiography. Coronary flow reserve was determined before and after successful PTCA in 20 patients with 1-vessel coronary artery disease (CAD). Ten other patients with angiographically normal coronary arteries, normal exercise electrocardiographic responses and normal cardiac structure also were evaluated. Coronary flow reserve was calculated as the ratio of papavarine-induced hyperemic flow to basal flow. Flow reserve for the stenotic artery in patients who underwent PTCA was 1.6 +/- 0.2 (mean +/- standard error of the mean) (range 0.9 to 3.9, n = 20). After successful PTCA, flow reserve for this artery increased to 3.1 +/- 0.2 (range 1.7 to 5.2, n = 20) (p less than 0.0001 vs before PTCA). Flow reserve for adjacent nonstenotic, nondilated arteries was 2.6 +/- 0.2 (range 1.4 to 4.5, n = 13). Coronary flow reserve in the stenotic arteries before PTCA was far below normal. In addition, both successfully dilated arteries and nondilated, nonstenotic arteries in these patients with CAD had flow reserve values smaller than those in the patients with normal arteries (4.8 +/- 0.6, range 2.3 to 12.6, n =22) (p less than 0.01). These findings suggest that digital angiographic determinations of coronary flow reserve can reveal important alterations of individual artery vasodilatory capacity. The data suggest that although an epicardial coronary in a patient with CAD may appear angiographically normal, flow reserve remains impaired due to abnormalities as yet undefined.

The effect of intravenous thrombolytic therapy on left ventricular function: a report on tissue-type plasminogen activator and streptokinase from the Thrombolysis in Myocardial Infarction (TIMI Phase I) trial

In Phase I of the NHLBI trial of Thrombolysis in Myocardial Infarction (TIMI), 290 patients admitted within 7 hr after onset of acute infarction were randomly assigned to intravenous treatment with either streptokinase (SK) or recombinant tissue-type plasminogen activator (rt-PA). Left ventricular function was measured from contrast ventriculograms in 145 patients with both pretreatment and predischarge studies analyzable. Regional wall motion in the infarct site was measured by the centerline method and expressed in units of standard deviations (SDs) from the mean motion in 52 normal subjects. Patients treated with rt-PA (n = 77) achieved a significantly higher reperfusion rate after 90 min of treatment. Perfusion of the infarct-related artery improved from visual grade 0 or 1 (total occlusion or penetration without perfusion) to grade 2 or 3 (partial or full reperfusion) in 62% receiving rt-PA vs 31% receiving SK (n = 68) (p less than .001). However, the ejection fraction did not change significantly from before treatment to before discharge in either treatment group (+0.7 +/- 6.7% vs +1.0 +/- 8.3%, respectively). A small but significant increase in regional wall motion was observed in each of the two groups (+0.4 +/- 0.8 vs +0.3 +/- 0.8 SD/chord, respectively; each p less than .001 compared with baseline). This was countered by declines in the hyperkinesis of the noninfarct region (-0.3 +/- 1.0 SD/chord [p = .01] compared with baseline and -0.2 +/- 1.0 SD/chord [p = .23], respectively). Analysis of the combined groups revealed that the ejection fraction increased only in patients who achieved reperfusion by 90 min after onset of therapy or who had subtotal occlusions initially. There was greater recovery of left ventricular function in patients who achieved reperfusion earlier vs later than 4 hr after symptom onset and in patients with vs without some collateral circulation to the infarct-related artery.

Thrombolytic therapy for prosthetic cardiac valve thrombosis

To determine the efficacy and safety of thrombolytic therapy for prosthetic valve thrombosis, a composite series of 41 patients who received either streptokinase or urokinase intravenously for this disorder were analyzed. The series comprised 3 patients treated at Rhode Island Hospital and 38 previously reported on. Short-term success was achieved in 32 patients (78%). Prosthetic valve thrombosis recurred in seven (22%) of the successfully treated patients, four of whom were retreated with thrombolytic therapy. A favorable clinical outcome was observed in each. Fever and venipuncture bleeding were the most frequent side effects. Systemic embolization occurred in 4 (15%) of 26 patients with either aortic or mitral prosthetic valve thrombosis. None of these latter patients experienced a permanent neurologic or circulatory deficit. It is concluded that thrombolytic therapy is of value in the treatment of prosthetic valve thrombosis.

A trial of the calcium antagonist nisoldipine in hypertensive non-insulin-dependent diabetic patients

The antihypertensive and metabolic effects of a new calcium antagonist nisoldipine (10 to 20 mg at night) were investigated in 14 mild to moderately hypertensive non-insulin-dependent diabetic patients (median age 62, range 50-70 years). In a 12-week placebo controlled single blind study, sitting and standing blood pressure were significantly lowered (p less than 0.001). Heart rate was unchanged as were blood urea, creatinine, bilirubin, mmol/l (mean +/- SEM) and uric acid concentrations. Plasma sodium levels fell during active therapy (142 +/- 0.5 mmol/l (mean +/- SEM) versus 139 +/- 0.5 (p less than 0.001) and remained lower during the washout period. Plasma calcium concentrations increased during nisoldipine therapy (2.41 +/- 0.02 versus 2.51 +/- 0.03 mmol/l, p less than 0.001) and returned towards baseline during the washout period. Plasma ionized calcium concentrations showed similar changes but plasma sodium and calcium remained within the normal laboratory ranges in all patients at all times. Serum triglyceride concentrations fell (placebo 1.9 +/- 0.02 mmol/l vs nisoldipine 1.6 +/- 0.2, p less than 0.05), but fasting cholesterol was unchanged. Fasting blood glucose, and the blood glucose response to oral glucose challenge (75 g) showed no differences though HbA1 concentrations fell (10.6 +/- 0.7 versus 9.2 +/- 0.05%, p less than 0.05) and tended to rise when the drug was withdrawn. Haemoglobin concentrations also fell during active therapy (14.7 +/- 0.4 vs 14 +/- 0.32 g/dl p less than 0.001) and also remained lower after the washout period (13.9 +/- 0.03 g/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of long-term clinical outcome with final translesional pressure gradient during coronary angioplasty

The final translesional pressure gradient measured during coronary angioplasty correlates with immediate angiographic and clinical results. Whether the pressure gradient is of value in predicting late clinical outcome has not been determined. We therefore obtained complete follow-up information on 159 patients with single-vessel disease who underwent successful coronary angioplasty. Mean follow-up time was 15 +/- 10 months. The occurrence of repeat angioplasty, coronary bypass surgery, recurrent anginal chest pain, or a positive postangioplasty stress test were considered clinical events indicative of late failure. Of the variables age, gender, initial and final translesional pressure gradient, extent of initial and final arterial narrowing, site of dilatation, type of balloon catheter used, number of inflations, and maximal inflation pressure, only the final translesional pressure gradient was predictive of late failure when analyzed by multivariate techniques. Thus, the final translesional pressure gradient is of value in predicting both immediate and late outcome after coronary angioplasty.

Sustained efficacy of percutaneous transluminal coronary angioplasty

To determine whether the immediate efficacy of percutaneous transluminal coronary angioplasty (PTCA) is sustained, follow-up data were obtained in 183 patients who had undergone PTCA at least 1 year earlier. The duration of follow-up ranged from 1 to 5 years. Subjective clinical information was obtained in each patient and objective functional information, determined by exercise stress testing, was obtained in 91. PTCA was initially successful in 141 patients (79%). Of the 42 patients in whom PTCA was unsuccessful, 26 underwent coronary artery bypass graft surgery (CABG), while 16 were maintained on medical therapy (MED). When compared to the MED patients at time of follow-up, successful PTCA patients experienced less angina (13% vs 47%; p = 0.003), used less nitroglycerin (25% vs 73%, p = 0.003), were hospitalized less often for chest pain (8% vs 31%; p = 0.02), and subjectively felt their condition had improved (96% vs 20%; p less than 0.001). Furthermore, during exercise testing, the prevalence of angina was reduced (9% vs 43%; p = 0.05), and exercise duration was greater (8.2 minutes vs 5.8 minutes, p = 0.05) among PTCA patients. There were no significant differences in the incidence of subsequent myocardial infarction, mortality, or need for coronary artery bypass surgery. For these variables, no differences were seen between the CABG and PTCA groups. Thus, successful PTCA results in long-term relief of subjective and objective manifestations of myocardial ischemia, superior to that of medical therapy and comparable to CABG.

Effect of intravenous and oral acebutolol in patients with bundle branch block

We studied the effect of intravenous (1 mg/kg) and oral (400 mg) acebutolol on atrioventricular conduction in 22 patients with idiopathic bundle branch block and 1 to 1 atrioventricular conduction. Seven patients had previously symptomatic complete heart block (Group 1) and 15 were asymptomatic with bundle branch block only (Group 2). Following intravenous acebutolol heart rate decreased 82 +/- 16 to 63 +/- 16/min (P less than 0.01), A-H interval lengthened 98 +/- 22 to 121 +/- 30 msec (P less than 0.005) and H-V time was prolonged 60 +/- 13 to 70 +/- 17 msec (P less than 0.02) in those with previous heart block. The corresponding changes in the patients with no previous block were 74 +/- 14 to 61 +/- 8/min (P less than 0.01), 90 +/- 17 to 109 +/- 22 msec (P less than 0.05) and 48 +/- 15 to 56 +/- 14 msec (P less than 0.01). There was no difference between the basal or induced changes between these two groups. After intravenous acebutolol infusion 2 of 6 patients with previous spontaneous heart block and none of those without previous heart block developed atrioventricular block distal to His. The induced block was temporary (less than 10 min) and corresponded to the time of peak plasma acebutolol levels. Temporary atrioventricular block followed oral acebutolol administration in 4/7 patients with previous spontaneous heart block and 0/14 in those without block. In patients with bundle branch block intravenous acebutolol prolonged H-V conduction times in 19/20 patients and intravenous and oral acebutolol induced A-V block in 4/7 patients with previous spontaneous block.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous recombinant tissue-type plasminogen activator in patients with acute myocardial infarction: a report from the NHLBI thrombolysis in myocardial infarction trial

The efficacy and safety of a 3 hr, 80 mg intravenous infusion of recombinant tissue-type plasminogen activator (rt-PA) were investigated in 47 patients with acute myocardial infarction. Coronary angiography, performed before the administration of rt-PA and for 90 min thereafter, demonstrated that 37 patients had total coronary occlusion before therapy. After 90 min of rt-PA (50 mg), reperfusion of the infarct-related artery was observed in 25 patients (68%). Continuous infusions of heparin for anticoagulation were administered for 8 to 10 days. Of 36 patients who underwent follow-up coronary cineangiography, 21 had initially presented with total occlusion and had experienced reperfusion at 90 min. Sustained perfusion of the infarct-related artery was observed in 14 (67%) of these 21 initially reperfused patients. Late angiography was performed in nine patients who initially demonstrated subtotal occlusion of the infarct-related artery; sustained perfusion was observed in eight (89%). Significant bleeding was observed in 15 patients (32%). A hematoma at the site of the acute catheterization accounted for most instances of significant bleeding (11/15, 73%). Administration of rt-PA resulted in a significant decline in fibrinogen and plasminogen while amounts of fibrin(ogen) degradation products rose. In no patient, however, did fibrinogen levels decline to less than 140 mg/dl. Thus, rt-PA, administered as a brief 80 mg intravenous infusion, is capable of restoring blood flow in a high proportion of patients with acute myocardial infarction due to total coronary obstruction. Declines in plasma fibrinogen and plasminogen are observed. If combined with heparin anticoagulation and invasive vascular procedures, significant bleeding is a common complication.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary flow reserve provided by sequential internal mammary artery grafts

Although internal mammary artery bypass grafts have a high patency rate, the adequacy of blood flow through such conduits, particularly if used sequentially, has been questioned. To evaluate this issue, coronary flow reserve was studied in 20 patients after coronary bypass surgery. Nine patients had sequential internal mammary grafts to the diagonal and left anterior descending coronary arteries; five had a single internal mammary graft to the left anterior descending artery and six had sequential saphenous vein grafts. Fifteen additional single vein grafts were also placed in these patients. Coronary flow reserve was measured after contrast-induced hyperemia by a digital subtraction angiographic technique an average of 25 days after surgery. There was no difference in coronary flow reserve between the proximal and distal anastomotic regions in either the sequential internal mammary graft group (2.14 +/- 0.50 versus 2.29 +/- 0.68, n = 8, p = NS) or the sequential vein group (1.77 +/- 0.49 versus 2.08 +/- 0.78, n = 6, p = NS). In addition, the flow reserve provided to either vascular bed of the sequential internal mammary graft was not different from that provided by a single internal mammary graft (1.64 +/- 0.39, n = 5), a single vein graft (1.95 +/- 0.95, n = 15) or nonstenotic native coronary arteries (2.04 +/- 0.87, n = 34). No cases of intracoronary steal were observed. Although some patients had unequal flow reserves between the proximal and distal anastomotic zones, these occurred in the setting of residual coronary stenoses distal to the site of graft insertion or prior myocardial infarction in the grafted distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated coronary vascular resistance in the presence of reduced resting blood flow distal to a severe coronary stenosis

Vascular reserve in underperfused myocardium has recently been described. This seemingly paradoxical observation conflicts with older concepts of the coronary circulation which hold that flow deficits do not develop until reserve is fully exhausted. To examine this phenomenon in greater detail in an animal model mimicking a fixed human coronary artery stenosis, we analysed the records of 25 carefully selected, sedated pigs all instrumented with a rigid intralumenal coronary stenosis (82% lumenal diameter reduction). Each animal satisfied the following criteria: 1) perfused myocardial mass beyond the stenosis was within a narrow weight range (16 to 24 g); and 2) post stenosis (distal) epicardial (Epi) and endocardial (endo) flows were less than or equal to 90% of respective flows in a region perfused by the non-stenosed circumflex (CX) coronary artery. Accordingly, distal flow was reduced compared to circumflex zone flow (p less than 0.01) in the Epi (173 +/- 51 to 113 +/- 32 ml . 100g-1 . min-1), Endo (146 +/- 39 to 116 +/- 27) and transmural (Tm) regions (164 +/- 45 to 124 +/- 31). Despite a flow deficit and constant severity of stenosis, distal zone Tm resistance (0.55 +/- 0.21 mmHg/ml . 100 g-1 . min-1) exceeded the minimum level achievable with intravenous infusion of adenosine (0.25 +/- 0.07) in a separate group of eight animals without a stenosis. Distal transmural resistance also varied over a five fold range (0.27 to 1.33) and in 20/25 animals exceeded the highest level (0.37) seen in non-stenosis animals during adenosine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation to the stress of tachycardia in patients with coronary artery disease: insight into the mechanism of the warm-up phenomenon

Adaptation to exercise or the "warm up phenomenon" has been observed in some patients with angina pectoris. To investigate adaptation, eleven patients with exertional angina pectoris and angiographic evidence of coronary artery disease underwent two identical bouts of sequential tachycardia stress separated by a brief recovery period. Manifestations of ischemia were less during the second stress, as evidenced by a reduction in the severity of angina pectoris, less ST segment depression, and improved lactate extraction. Peak coronary blood flow during the second stress (81 +/- 20 ml/min) was not significantly different from that during the first (95 +/- 32 ml/min). Regional myocardial oxygen consumption, however, was significantly (p = .03) lower during the second stress (8.8 +/- 2.4 ml O2/min) when compared with the first (11.4 +/- 3.0 ml O2/min). Thus, patients with coronary artery disease can develop anginal tolerance to the stress of tachycardia similar to that observed after repeated bouts of exercise. A relative reduction in myocardial oxygen consumption, rather than an increase in coronary blood flow, appears to account for this phenomenon.

Evidence against significant resting alpha-adrenergic coronary vasoconstrictor tone

The importance of sympathetically mediated coronary vasoconstrictor tone as a determinant of resting coronary blood flow was assessed in the conscious dog by comparing blood flow and oxygen extraction in a normally innervated (I) and a previously sympathectomized (Sx) region of the same left ventricle. The regional ventricular sympathectomy was achieved by the topical application of phenol. The animals were well acclimated to the laboratory environment before regional myocardial blood flow was measured with microspheres or regional myocardial oxygen extraction was determined on blood sampled from chronically implanted coronary venous catheters. Results indicated that blood flow and oxygen extraction were not significantly different in I and Sx regions under these conditions. Regional blood flow data obtained after beta-adrenergic blockade or combined alpha- and beta-adrenergic blockade were not significantly different from control data. Thus we were unable to confirm previous evidence in the literature of significant resting sympathetic coronary vasoconstrictor tone in the conscious animal.

Recovery of myocardial function following brief versus prolonged atrial pacing stress in the presence of coronary artery stenosis

The ability of myocardium distal to a severe coronary artery stenosis to recover from brief (5 min) versus prolonged (30 min) atrial pacing stress was compared in this study. Eight closed chest pigs were prepared with a coronary artery stenosis (82% lumenal diameter reduction) in the left anterior descending artery and ultrasonic length sensors in left anterior descending endocardium. Extent of recovery of systolic function 5 min following a brief (5 min) period of ischaemia induced by rapid (175 to 190 min-1) atrial pacing (AP-1) was compared with that following a prolonged (30 min) period of ischaemia induced by rapid atrial pacing (AP-2). Regional myocardial blood flow (ml X min-1 X g-1) was measured at control, during, and following atrial pacing. Regional shortening (%) distal to the stenosis declined versus control at both 5 min of AP-1 (10.0 +/- 7.3 (mean +/- 1 SD) to 0.6 +/- 0.9, p less than 0.01) and 30 min of AP-2 (6.8 +/- 3.3 to 2.1, +/- 3.5, p less than 0.01). However, within 5 min of discontinuing both brief as well as prolonged pacing, regional segmental shortening (5.7 +/- 3.9 and 7.0 +/- 6.9, respectively) returned to 50 to 70% of initial control levels (10.0 +/- 7.3). Regional shortening was similar 5 min following brief and prolonged stress. Distal left anterior descending zone epicardial regional myocardial blood flow increased (p less than 0.01) versus control at AP-1 (1.05 +/- 0.24 to 1.39 +/- 0.24) and 30 min of AP-2 (0.99 +/- 0.21 to 1.40 +/- 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of repeat percutaneous transluminal coronary angioplasty for coronary restenosis

The short- and long-term outcome of patients within the NHLBI PTCA Registry who underwent repeat PTCA for coronary restenosis were analyzed. Of 1,880 patients in whom an initial PTCA was successful, 203 had a repeat PTCA attempted after restenosis developed. Repeat PTCA was usually performed within 6 months of the first procedure. The success rate of repeat PTCA was 85.2%. As a direct result of repeat PTCA, 1.5% of patients had an MI and 2% required emergency CABG. No patient died as a result of the attempted second procedure. One to 3 years of follow-up information was available in 94% of eligible patients. Most patients (75.9%) did not have a subsequent (third) PTCA, CABG or an MI. The late mortality rate was 0.8%. Angiographic follow-up information was available in 62 patients. Sustained enhancement of the diameter of the redilated lesion was observed in 66%. Thus, repeat PTCA has a high success and a low complication rate. Most patients did not have subsequent restenosis and are free of angina. Hence, repeat PTCA should be recommended for patients who have restenosis and should be considered as an integral component of PTCA therapy.

Contrasting effects of nifedipine and adenosine on regional myocardial flow distribution and metabolism distal to a severe coronary arterial stenosis: observations in sedated, closed-chest, domestic swine

This study tested the hypothesis that intrinsic negative inotropic effects of a drug used to induce coronary vasodilation distal to a severe coronary arterial stenosis may influence the extent of redistribution of transmural flow and its metabolic consequences. To test this hypothesis, studies were conducted in eight closed-chest, sedated swine with severe (82% reduction in luminal diameter) coronary arterial stenoses. Measurement of hemodynamic parameters, regional myocardial blood flow (microsphere technique), lactate metabolism, and oxygen consumption were made (1) under control conditions, (2) after 10 min of intracoronary infusion of a vasodilator distal to the stenosis, and (3) under repeat control conditions. Each animal received both intracoronary adenosine (400 micrograms/min) and nifedipine (50 micrograms/min). The order of drug infusion was chosen at random and a control period separated administration of each. In response to nifedipine there was no significant change in the group mean (+/- SD) value of endocardial flow (1.21 +/- 0.34 to 1.29 +/- 0.61 ml/min X g-1) distal to the stenosis. In contrast, epicardial flow increased in comparison with control in response to nifedipine (1.30 +/- 0.58 to 1.79 +/- 0.74 ml/min X g-1; p less than .05). Regional myocardial oxygen consumption (MVO2) declined in comparison with control in response to nifedipine (14.0 +/- 4.2 to 11.1 +/- 5.0 ml/min X 100 g-1; p less than .05). Regional lactate extraction did not change in comparison with control during infusion of nifedipine (18.2 +/- 22.4 vs 11.7 +/- 16.8). In response to adenosine, endocardial blood flow distal to the stenosis declined in comparison with control (1.25 +/- 0.53 to 1.07 +/- 0.38 ml/min X g-1; p less than .05), while epicardial flow increased (1.31 +/- 0.55 to 2.26 +/- 0.59 ml/min X g-1; p less than .01). Regional MVO2 also tended to decline in comparison with control in response to adenosine (13.4 +/- 4.9 to 11.7 +/- 2.9 ml/min X 100 g-1) and was significantly (p less than .05) reduced in comparison with postintervention control (14.6 +/- 4.2 ml/min X 100 g-1). In contrast to nifedipine, adenosine caused a significant decline in regional lactate extraction in comparison with control (12.7 +/- 23.2% to -40.6 +/- 55.0%; p less than .01). Thus, administration of nifedipine, a negative inotropic agent, resulted in (1) a decline in regional MVO2, (2) increased epicardial blood flow with variable effects on endocardial flow distal to the stenosis, and (3) no evidence of de novo or worsening ischemia, even in animals in which endocardial flow decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

Follow-up assessment of St. Jude Medical prosthetic valve in the tricuspid position: clinical and hemodynamic results

Seven patients underwent postoperative right heart catheterization implantation of the St. Jude Medical prosthetic valve in the tricuspid position. Six patients were in atrial fibrillation at catheterization, and 1 was in normal sinus rhythm. At postoperative catheterization, the mean right atrial pressure ranged between 4 and 16 mm Hg (mean, 9.7 mm Hg); right ventricular systolic pressure was normal in 1 patient, mildly elevated (less than 50 mm Hg) in 4 patients, and moderately elevated (65 and 70 mm Hg) in 2. The cardiac output ranged between 3.0 and 7.0 L/min (mean, 4.2 L/min). There was no end-diastolic gradient across the St. Jude Medical prosthesis in 6 patients. The other patient had a gradient of 2 mm Hg across the valve when cardiac output was 7.0 L/min. On fluoroscopy, both discs demonstrated full excursion in all patients. These data demonstrate that a normally functioning St. Jude Medical valve in the tricuspid position does not create obstruction to forward flow, and they support use of this prosthesis in patients with tricuspid valve disease.