Andréa Falcão

The Effects of Glibenclamide, a KATP Channel Blocker, on the Warm-Up Phenomenon

Background: The warm‐up phenomenon observed after the second of two sequential exercise tests is characterized by an increased time to ischemia and ischemic threshold, and the latter is related to ischemic preconditioning. Previous studies have demonstrated that a single dose of glibenclamide, a cardiac ATP‐sensitive K (KATP) channel blocker, prevents ischemic preconditioning. This study aimed to investigate the effects of chronic treatment with glibenclamide during two sequential exercise tests.

Exercise stress testing before and after successful multivessel percutaneous transluminal coronary angioplasty

Controversy exists regarding the diagnostic accuracy, optimal technique, and timing of exercise testing after percutaneous coronary intervention. The objectives of the present study were to analyze variables and the power of exercise testing to predict restenosis or a new lesion, 6 months after the procedure. Eight-four coronary multi-artery diseased patients with preserved ventricular function were studied (66 males, mean age of all patients: 59 +/- 10 years). All underwent coronary angiography and exercise testing with the Bruce protocol, before and 6 months after percutaneous coronary intervention. The following parameters were measured: heart rate, blood pressure, rate-pressure product (heart rate x systolic blood pressure), presence of angina, maximal ST-segment depression, and exercise duration. On average, 2.33 lesions/patient were treated and restenosis or progression of disease occurred in 46 (55%) patients. Significant increases in systolic blood pressure (P = 0.022), rate-pressure product (P = 0.045) and exercise duration (P = 0.003) were detected after the procedure. Twenty-seven (32%) patients presented angina during the exercise test before the procedure and 16 (19%) after the procedure. The exercise test for the detection of restenosis or new lesion presented 61% sensitivity, 63% specificity, 62% accuracy, and 67 and 57% positive and negative predictive values, respectively. In patients without restenosis, the exercise duration after percutaneous coronary intervention was significantly longer (460 +/- 154 vs 381 +/- 145 s, P = 0.008). Only the exercise duration permitted us to identify patients with and without restenosis or a new lesion.

Chagas' Disease: Update on Current Diagnosis

Purpose of ReviewChagas’ disease has become an emerging health problem due to increased migration. In the present review, we have summarized the usefulness of non-invasive imaging tools for the diagnosis of cardiac involvement in Chagas’ disease, with emphasis on modern technologies. M-mode, bidimensional (2-D), and three-dimensional (3-D) echocardiographies may allow the evaluation of left ventricular (LV) regional and global contractile function, right ventricle (RV) impairment, evidence of aneurysms and thrombi, and assessment of diastolic function in any stage of the disease.Recent FindingsNew modalities such as strain and speckle-tracking imaging have brought non-invasive indices to the understanding of the mechanisms of cardiac dyssynchrony. The assessment of cardiac autonomic denervation using 123I-metaiodobenzylguanidine (123I-MIBG), LV, and RV systolic function and the study of LV mechanical dyssynchrony by gated cardiac blood pool are available in current nuclear imaging for patients with Chagas’ disease. The findings of myocardial fibrosis by cardiac magnetic resonance (CMR), mainly in inferolateral regions, are a marker of subclinical involvement and worse prognosis in Chagas’ disease, even in patients with preserved ventricular function.SummaryThe detection and quantification of early signs of heart involvement by new technologies should be useful for risk stratification and in the clinical decision process for new therapeutic methods and could improve the natural history of the disease.

INFLUENCE OF LEFT BUNDLE BRANCH BLOCK IN ASSESSMENT OF MYOCARDIAL BLOOD FLOW FROM RUBIDIUM 82 POSITRON EMISSION TOMOGRAPHY IMAGING

Perfusion defects are frequent in myocardial scintigraphy in left bundle branch block (LBBB) patients. However, scarce studies show decreased coronary flow reserve (CFR) in the left anterior descending artery territory, regardless of the presence of coronary artery disease (CAD). We sought to

Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

OBJECTIVES: Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease. OBJECTIVE: We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block. METHODS: Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII). RESULTS: Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001). CONCLUSION: The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with left bundle branch block.

The heart rate recovery may be influenced by the ischemic preconditioning

Introduction: The warm-up phenomenon, observed after the second of two sequential exercise tests, is characterized by an increased of both time to lschemia and ischemic threshold, and the last one is probably related to a ischemic preconditioning. In the other hand, the heart-rate recovery immediately after exercise, which may be a reflection of decreased vagal activity. is a powerful predictor of overall mortality. This study aimed to Investigate the effects of ischemic preconditioning on the heart-rate recovery during the first minute after graded exercise. Methods: Twenty patients with chronic stable angina pectoris were enrolled and all were off treatment. They underwent two consecutive treadmill exercise tests according to the Bruce protocol with recovery period behveen the tests of 30 min to re-establish baseline conditions. The value for the recovery of heart rate was defined as the reduction in the heart rate from the peak exercise to the rate one minute after the cessation of exercise. Results: The hearl rate and the rate-pressure product at l.Omm ST-segment depression significantly increased during the second exercise test compared to the first (121.3 + 16.5 vs.127.3 + 15.3 beatslmin, pcO.001, and 216.7 + 43.1 vs. 232.1 + 43.0 beats.mmHg.l@/min, pcO.001): the time to 1.0 mm ST-segment depression d&g the second exercise test was greater than that during the first test, too (225.0 -+ 112.5 vs. 267.02 122.3 s, p=O.OOG).The median heati rate recovery increased significantly during the second test compared to the first (254213.5 vs. 29.4 + 15.0 beatslmin, p=O.O2). Conclusion: The main findings of this study are an improvement of the ischemic threshold in the second test probably related to ischemlc preconditioning and an improvement of the heart-rate recovery. Although there isn’t a clear explanation of this relation, it is clear that ischemic preconditioning represents a powerful protective phenomenon and the better heart rate recovery in the second compared to the first test may be a expression of this phenomenon.