Prasad, Abhiram

A significant proportion of patients with ST-elevation myocardial infarction have persistent impairment of microvascular blood flow despite successful reperfusion of epicardial vessels. Microvascular dysfunction has been associated with larger infarct size, increased predisposition to ventricular arrhythmias, heart failure, cardiogenic shock, recurrent myocardial infarction, and death. It remains unclear whether this association is of direct mechanistic significance or whether the microcirculatory injury is an epiphenomenon and a manifestation of greater ischemic insult to the myocardium. Although several potential mechanisms have been proposed for the microvascular dysfunction, distal microembolization during mechanical reperfusion is likely to be an important contributor. Consequently, there has been increasing interest in the concept of adjunctive mechanical thrombectomy to improve outcomes in primary percutaneous coronary intervention. Until recently, randomized trials of thrombectomy and distal protection devices during primary percutaneous coronary intervention have provided conflicting results with no definitive evidence for efficacy. The recently published Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction Study has rekindled the interest in this area. This trial is the largest randomized study of a thrombectomy device published to date and demonstrates that adjunctive treatment with aspiration thrombectomy during primary percutaneous coronary intervention improves surrogate and clinical end points. The aim of the present report is to review the evidence to date on the role of mechanical thrombectomy and embolic protection in native coronary arteries during primary percutaneous coronary intervention.

Background— Myonecrosis after percutaneous coronary intervention (PCI) has been correlated with a worse prognosis, but controversy exists about the clinical significance and potential mechanisms for the association. The aim of this study was to evaluate the relative impact of preprocedural and postprocedural cardiac troponin T (cTnT) levels on survival rate after PCI. Methods and Results— We evaluated 5487 patients from the Mayo Clinic registry who required nonemergency PCI, and we examined the relationship between periprocedural cTnT levels, with the 99th percentile cutoff value used for normal (<0.01 ng/mL), and outcomes. The patients were divided into 3 groups: normal preprocedural and postprocedural cTnT levels (no myonecrosis), normal preprocedural but elevated postprocedural cTnT levels (PCI-related myonecrosis), and abnormal preprocedural cTnT. The 30-day death rates were 0.1%, 0.6%, and 2.3%, respectively, in the 3 groups. In a multivariable model, an abnormal pre-PCI cTnT level (hazard ratio 9.66 [2.30–40.57]; P =0.002), and PCI-related myonecrosis (4.71 [1.02–21.83]; P =0.048) were independent predictors of 30-day mortality. Over a median follow-up of 28 months, an abnormal pre-PCI cTnT level (hazard ratio 1.79 [1.35–2.39]; P <0.001) independently predicted death, but the occurrence of PCI-related myonecrosis did not. A postprocedural elevation in creatine kinase MB fraction was not an independent predictor of long-term risk of death (0.912 [0.70–1.19]; P =0.5). Conclusions— A preprocedural cTnT level >0.01 is a powerful independent predictor of prognosis after PCI and is of greater prognostic significance than the postprocedural biomarker levels. PCI-related myonecrosis occurs frequently and predicts short-term but not long-term risk of death.

Endothelin plays an important role in the pathogenesis of atherosclerosis. The aim of the study was to evaluate the safety and hemodynamic and metabolic responses to 6 months treatment with atrasentan, the selective endothelin-A receptor antagonist. Seventy-two patients with multiple cardiovascular risk factors and nonobstructive coronary artery disease on coronary angiogram were randomly assigned in a double-blind manner to atrasentan or placebo. Mean aortic blood pressure decreased from 92±10 to 80±10 mm Hg ( P <0.001) in the atrasentan group and did not change in the placebo group (93±10 and 92±11 mm Hg; P =0.84). The difference between the groups was significant ( P <0.001). No effect on heart rate was observed. In a subgroup of patients not treated with angiotensin-converting enzyme inhibitor, creatinine level decreased in the atrasentan versus the placebo group ( P =0.011). Fasting glucose ( P =0.026), glycosylated hemoglobin level ( P =0.041), triglyceride l ( P =0.013), lipoprotein-A ( P =0.046), and uric acid levels ( P =0.048) decreased significantly in the atrasentan group compared with the placebo group. No progression of angiographic coronary disease was observed. The most common adverse effects with atrasentan were nasal stuffiness, headache, and edema. In conclusion, 6 months of treatment with atrasentan results in a reduction of blood pressure and improvement in glucose and lipid metabolism. These findings suggest the beneficial role of atrasentan in the treatment of hypertension and metabolic syndrome.

In vitro and animal studies suggest that oxidative stress is associated with endothelial dysfunction. We tested whether local oxidative stress and nitric oxide (NO) bioavailability in the coronary circulation is associated with coronary endothelial dysfunction in humans. Blood samples were obtained simultaneously from the left main coronary artery and the coronary sinus for measurement of F2-isoprostanes, myeloperoxidase, nitrotyrosine, and superoxide dismutase in 20 patients without significant coronary disease. Afterward, coronary blood flow and the vascular response to intracoronary acetylcholine and N G -monomethyl- L -arginine (L-NMMA) were assessed. The gradient of isoprostanes between the arterial levels and coronary sinus correlated with the change in coronary artery diameter in response to acetylcholine ( r =−0.79, P <0.0001). Isoprostanes net production across the left anterior descending artery territory correlated with a decrease in superoxide dismutase activity ( r =0.66, P =0.002) and decrease in coronary artery diameter in response to L-NMMA (r s =0.48, P <0.05). Myeloperoxidase and nitrotyrosine gradients were similar in patients with endothelial dysfunction and controls. The effect of L-NMMA was similar in both groups. We conclude that coronary endothelial dysfunction in humans is characterized by local enhancement of oxidative stress without a decrease in basal NO release. This study supports the hypothesis that local oxidative stress has a role in reduction of NO bioavailability in humans with coronary endothelial dysfunction.

Background— Little is known about the impact of technological and pharmacological advances on long-term outcome after percutaneous coronary intervention in general clinical practice. Methods and Results— We analyzed in-hospital and long-term outcome of 24 410 percutaneous coronary interventions among 18 575 unique patients who underwent percutaneous coronary intervention at Mayo Clinic over 25 years. The study population was divided into group 1 (n=3708), coronary interventions from 1979 to 1989; group 2 (n=7020), interventions from 1990 to 1996; group 3 (n=10 952), interventions from 1996 to 2003; and group 4 (n=2730), interventions from 2003 to 2004. Despite the fact that patients in groups 3 and 4 were significantly older, sicker, and had greater prevalence of comorbid conditions, heart failure, and previous revascularization than those in groups 1 and 2, procedural success in groups 3 and 4 improved significantly (94%) versus groups 2 (89%) and 1 (78%) ( P <0.001). Significant reduction in in-hospital mortality (groups 4 to 1: 1.8%, 1.7%, 2.6%, 3.0%; P <0.001) and need for emergency bypass surgery (groups 4 to 1: 0.4%, 0.5%, 1.6%, 5%; P <0.001) was noted in groups 3 and 4 compared with groups 1 and 2. Better adherence to currently recommended evidence-based medications for secondary prevention was seen in the recent time periods. After adjustment, significant reduction in follow-up mortality (hazard ratio, 0.81 and 0.74 for groups 3 and 4, respectively); death or myocardial infarction (hazard ratio, 0.80 and 0.75 for groups 3 and 4, respectively); death, myocardial infarction, or revascularization (hazard ratio, 0.76 and 0.58 for groups 3 and 4, respectively) was noted in recent time periods. Conclusions— Despite higher-risk profiles of patients who underwent percutaneous coronary intervention in recent time periods, procedural success as well as in-hospital and long-term outcomes improved significantly over the last 25 years.