Biochemical changes as a result of prolonged strenuous exercise.

OBJECTIVE: To briefly review biochemical changes that may result from prolonged strenuous exercise and to relate these changes to health risk. METHODS: Medline and Sports Discus databases were searched for relevant articles. Additional articles were found using cross referencing and the authors' knowledge of the subject area. RESULTS: Prolonged strenuous exercise may result in a series of biochemical changes that are of concern from a health point of view. Generally, these changes are benign, but some, especially hyponatraemia, are potentially life threatening occurrences. CONCLUSION: Doctors and athletes should be aware of the potentially adverse biochemical changes, especially hyponatraemia, that may result from prolonged strenuous exercise.

Increased circulating monocyte activation in patients with unstable coronary syndromes.

OBJECTIVES: The primary objective of this research was to assess the activation level of circulating monocytes in patients with unstable angina. BACKGROUND: Markers of systemic inflammatory responses are increased in patients with unstable coronary syndromes, but the activation state and invasive capacity of circulating monocytes have not been directly assessed. METHODS: Peripheral blood mononuclear cell (MC) activation in blood samples isolated from patients with stable and unstable coronary artery disease was measured in two studies. In study 1, a modified Boyden chamber assay was used to assess spontaneous cellular migration rates. In study 2, optical analysis of MC membrane fluidity was correlated with soluble CD14 (sCD14), a cellular activation marker. RESULTS: Increased rates of spontaneous monocyte migration (p < 0.01) were detected in patients with unstable angina (UA) (Canadian Cardiovascular Society [CCS] angina class IV) on comparison to patients with acute myocardial infarction (MI), stable angina (CCS angina classes I to III) or normal donors. No significant increase in lymphocyte migration was detected in any patient category. Baseline MC membrane fluidity measurements and sCD14 levels in patients with CCS class IV angina were significantly increased on comparison with MCs from normal volunteers (p < 0.001). A concomitant reduction in the MC response to activation was detected (p < 0.05). CONCLUSIONS: Using two complementary assays, activated monocytes with increased invasive capacity were detected in the circulation of patients with unstable angina. This is the first demonstration of increased monocyte invasive potential in unstable patients, raising the issue that systemic inflammation may both reflect and potentially drive plaque instability.

Predicting and explaining cardiac rehabilitation attendance.

BACKGROUND: A variety of factors influence patients' health behaviour; these are patterns of practitioner practice, patient characteristics and availability of resources. OBJECTIVES: To examine patient-related factors (demographic, health, psychosocial characteristics) that may influence patients' attendance at cardiac rehabilitation programs and their subsequent behaviour change. PATIENTS AND METHODS: A prospective cohort design was used. Three hundred four acute myocardial infarction and/or coronary artery bypass graft surgery patients from a tertiary care centre in a Western Canadian city were enrolled to participate in telephone interviews at two weeks and again at approximately six months after their hospital discharge. Measures of self-efficacy and behaviour performance for cardiac health maintenance and role resumption, motivation and social support were used at both interview times. A survey focusing on factors influencing patients' choices to attend cardiac rehabilitation programs was also administered at the interview six months after discharge. RESULTS: Attendance at cardiac rehabilitation programs is not associated with patients' risk factor status, and elderly and rural-living patients are at particular risk for nonattendance. CONCLUSIONS: Systematic mechanisms to guide the appropriate referral of patients to this health care resource and administer secondary prevention initiatives to those with limited access to resources need to be a priority in cardiovascular health care.

Psychosocial components of cardiac recovery and rehabilitation attendance.

OBJECTIVE: To examine the relations between demographic factors, specific psychosocial factors, and cardiac rehabilitation attendance. DESIGN: Cohort, repeated measures design. SETTING: A large tertiary care centre in western Canada PATIENTS: 304 consecutive consenting patients discharged following acute myocardial infarction and/or coronary artery bypass graft surgery. MAIN OUTCOME MEASURES: The Jenkins self-efficacy expectation scales and activity checklists of behaviour performance for maintaining health and role resumption, modified version of the self-motivation inventory, and the shortened social support scale. RESULTS: Those who had higher role resumption behaviour performance scores at two weeks after discharge were significantly less likely to attend cardiac rehabilitation programmes. At six months after discharge, those who attended cardiac rehabilitation demonstrated higher health maintenance self-efficacy expectation and behaviour performance scores. Health maintenance self-efficacy expectation and behaviour performance improved over time. Women reported less social support but showed greater improvement in health maintenance self-efficacy expectation. Changes in self-efficacy scores were unrelated to-but changes in health maintenance behaviour performance scores were strongly associated with-cardiac rehabilitation attendance. CONCLUSIONS: Cardiac patients and practitioners may have misconceptions about the mandate and potential benefits of rehabilitation programmes. Patients who resumed role related activities early and more completely apparently did not see the need to "rehabilitate" while those who attended cardiac rehabilitation programmes enhanced their secondary prevention behaviours.

Effects of half ironman competition on the development of late potentials.

OBJECTIVES: The primary purpose was to evaluate the prevalence of late potentials (LPs) in triathletes before and after a half ironman triathlon. The secondary purpose was to examine whether LPs are the electrocardiographic expression of a greater myocardial mass. METHODS: Nine asymptomatic male triathletes (mean age +/- SD, 32 +/- 5 yr) were examined using signal-averaged ECG (SAECG) 48-72 h before (PRE), immediately after (POST), and 24-48 h after the completion (RECOVERY) of a half ironman triathlon. Late potentials were considered to be present if two of the following SAECG anomalies were observed: 1) a prolonged filtered QRS (/QRS) complex (> or = 114 ms), 2) a lengthened low amplitude signal (LAS) duration (>38 ms), and/or 3) a low root mean square (RMS) voltage of the last 40 ms of the fQRS (<20 microV). Left ventricular dimensions were determined at PRE using M-mode echocardiography. RESULTS: There were no significant differences between PRE, POST, and RECOVERY in the fQRS duration, the LAS duration, or the RMS voltage. Two athletes displayed a single SAECG abnormality during PRE and two SAECG anomalies (i.e., LPs) during POST. Late potentials remained in one of the two athletes during RECOVERY. A moderate relationship existed between fQRS and left ventricular mass (r = 0.67, P < 0.05). CONCLUSIONS: Ultra-endurance training and/or events do not lead to LPs in the majority of triathletes who do not possess ventricular arrhythmias. However, a small subset of triathletes do display SAECG anomalies, which are augmented by an ultra-endurance event and may persist even after recovery from the event. Left ventricular mass does not affect overall SAECG parameters.

Effects of long term resistance training on left ventricular morphology.

OBJECTIVES: To assess the effects of long term (mean +/- SD 10+/-5 years, range three to 25 years) resistance training on left ventricular (LV) dimensions and mass. METHODS AND RESULTS: The study participants were 21 elite male power-lifters (age 33.4+/-5.9 years) and 10 sedentary male control subjects (age 30.9+/-4.2 years). Two-dimensionally guided transthoracic M-mode echocardiograms were obtained at rest to quantify LV diastolic cavity dimension, posterior wall thickness, ventricular septal wall thickness and LV mass. Long term resistance training was not associated with an alteration in LV diastolic cavity dimension (resistance trained 54. 4+/-4.3 mm versus control 51.8+/-5.6 mm), ventricular septal wall thickness (resistance trained 9.7+/-1.0 mm versus control 10.1+/-0.7 mm), posterior wall thickness (resistance trained 9.6+/-1.5 mm versus control 9.3+/-1.4 mm) or LV mass (resistance trained 200. 3+/-32.5 g versus control 186.5+/-39.6 g). In addition, no resistance-trained athlete was found to have an LV mean wall thickness above clinical normal limits (12 mm or less). CONCLUSION: Contrary to common beliefs, long term resistance training as performed by elite male power-lifters does not alter LV morphology.

ARCTIC: assessment of haemodynamic response in patients with congestive heart failure to telmisartan: a multicentre dose-ranging study in Canada.

BACKGROUND: The aim of this study was to examine the acute hemodynamic and neurohormonal effects of the angiotensin II antagonist telmisartan relative to placebo in patients with chronic symptomatic (New York Heart Association class II to III) congestive heart failure and to explore the dose-response relation for these effects. METHODS AND RESULTS: After baseline hemodynamic and neurohormonal measurements made with the use of a pulmonary artery and radial arterial catheter, 82 patients were randomly assigned to placebo or 10, 20, 40, or 80 mg of telmisartan in a double-blind fashion. Hemodynamic and neurohormonal measurements were carried out over 24 hours. Telmisartan caused significant decreases in systemic arterial, pulmonary arterial, and pulmonary capillary wedge pressures with evidence of a dose-response relation for each of these parameters. The drug had no significant effects on heart rate, cardiac index, or systemic vascular resistance. Telmisartan did not have consistent effects on either plasma norepinephrine or plasma atrial natriuretic peptide levels, although it did cause significant increases in both plasma renin activity and angiotensin II levels at higher doses. CONCLUSIONS: The acute administration of the angiotensin II antagonist telmisartan was associated with significant dose-dependent reductions in systemic arterial blood pressure and pulmonary pressures. Long-term follow-up studies are required to translate changes in hemodynamic parameters into a clinical benefit.

Cardiac rehabilitation: the forgotten intervention.

OBJECTIVE: To examine the influence of cardiac patients' demographic and health characteristics on physicians' cardiac rehabilitation (CR) referral practice and patients' attendance at such programs. DESIGN: A retrospective, systematic review of consecutive health records. SETTING: A tertiary care centre and the two associated CR programs in a Western Canadian city. PATIENTS: One thousand, three hundred and twenty-eight adult patients (21 years of age or older) discharged following acute myocardial infarction, percutaneous transluminal coronary angioplasty (PTCA) and/or coronary artery bypass graft surgery between September 1, 1996 and August 31, 1997. MAIN RESULTS: There were 1245 surviving patients. Evidence of attendance at a CR program was 28.4%, while auditable evidence of referral to a CR program was 23.9%. Stepwise logistic regression revealed that ability to speak English (OR 9.56) living in a city (OR 3.97) and current smoking (OR 1.51) were associated with an increased likelihood, whereas having a history of chronic obstructive pulmonary disease or asthma (OR 0.53), being 70 years of age or older (OR 0.42), having a current admission for PTCA (OR 0.32) and having a history of neurological or cognitive impairment (OR 0.26) were associated with a decreased likelihood of CR attendance. Sex, nature of coronary artery disease risk factors, incidence of postevent complications and pre-event cardiac status (including New York Heart Association status and number of previous events) were not associated with patients' CR attendance. CONCLUSIONS: This study suggests that there is an inconsistent and poorly documented approach to referral of patients to CR programs for reasons that remain unclear. These findings provide a foundation for development and testing of enhanced referral mechanisms and of innovative means to provide rehabilitation services to patients who are at risk for not being referred to or attending CR programs.

Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise. Part II: Novel techniques and new advances.

For exercise physiologists and sport cardiologists, one of the greatest challenges is to develop a valid, reliable, noninvasive and affordable measure of cardiac output (Q). There are several techniques available to measure Q during exercise conditions. These procedures generally provide accurate and reliable determinations of Q during submaximal exercise, but may be limited during maximal exercise conditions. The most commonly used noninvasive measures are the acetylene (C2H2) and carbon dioxide (CO2) rebreathe methods as reviewed in part I of this article. Only the foreign gas rebreathe method, using C2H2, meets all of the criteria of being noninvasive, easy to use, reliable and valid for use during maximal exercise. New methodologies have recently been developed to measure Q during exercise conditions. Although not as popular as the C2H2 and CO2 rebreathe methods, these methods have increasingly gained favour in exercise physiology and sport cardiology settings. The majority of these measures (if performed meticulously), with the exception of impedance cardiography, provide reasonably accurate and reliable determinations of Q. However, the cost of usage and technological limitations during maximal exercise have prevented these techniques from replacing the conventional measures of Q during exercise conditions. Doppler echocardiography and the modified C2H2 methods hold promise for the assessment of Q during maximal exercise. With further advances in these technologies their use in exercise physiology and sport cardiology setting may become more common.

Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise. Part I: Conventional techniques.

The assessment of cardiac function, particularly cardiac output (Q) during heavy exercise is essential for the evaluation of cardiovascular factors that might limit oxygen transport. A series of invasive and noninvasive techniques has been developed for the assessment and monitoring of Q during resting and submaximal exercise conditions. However, very few techniques have been found to give accurate and reliable determinations of Q during vigorous to maximum exercise. For exercise physiologists and sport cardiologists, maximal exercise data are of primary importance. The 'gold standard' measures of cardiac function are considered to be the direct Fick and dye-dilution methods. These have been widely shown to give accurate and reliable determinations of Q during resting and submaximal exercise conditions; however, their use during maximal exercise conditions is debatable due to the inherent risks involved with each and their increasing inaccuracy during the later stages of vigorous exercise. Thermodilution has also been considered to be a relatively good method for the determination of Q during rest and exercise conditions, but recent authors have questioned its use due to the nature of the measure and its inaccuracy during strenuous exercise. Various noninvasive measures of cardiac function have been developed to overcome the problems associated with the 'gold standard' measures. The first part of this article discusses conventional techniques used in exercise physiology settings. The majority of these provide accurate and reliable determinations of Q during rest and submaximal exercise. However, very few techniques are suitable for maximal exercise conditions. Perhaps only the foreign gas rebreathe using acetylene (C2H2) meets all the criteria of being noninvasive, simple to use, reliable over repeated measurements, accurate and useful during maximal exercise.

Limitation of left ventricular hypertrophy and dysfunction by ACE inhibition after anterior Q-wave myocardial infarction.

To determine whether limitation of left ventricular (LV) hypertrophy with angiotensin-converting enzyme inhibition after myocardial infarction (MI) is associated with improved systolic and diastolic function, quantitative two-dimensional echocardiograms and Doppler of 40 patients, who were randomized on day 3 after a first Q-wave anterior MI to receive therapy with captopril (12.5 mg t.i.d.) or placebo for 6 weeks, were analyzed for LV volumes (Simpson's rule) and mass (3D reconstruction), remodeling parameters and peak early (E) and late (A) transmitral flow velocities and deceleration times (DT) at 3 days, 6 weeks, 6 months and 1 year. Compared to placebo over 1 year, captopril limited (p < 0.001) the increase in diastolic volume and mass, increased LV ejection fraction and diastolic E/A ratio, and decreased DT, the frequency of E and A reversal, infarct expansion and aneurysm frequency but volume/ mass ratio was unchanged. Captopril over the first 6 weeks after a first Q-wave anterior MI limited LV remodeling and hypertrophy and improved both systolic and diastolic function up to 1 year.

Prognostic value of myocardial perfusion imaging with exercise and/or dipyridamole hyperemia in patients with preexisting left bundle branch block.

UNLABELLED: The detection of myocardial ischemia in patients with preexisting left bundle branch block (LBBB) remains problematic. Pharmacologic hyperemia with dipyridamole is now used routinely in such patients for detection of significant coronary artery disease. Little data exists on the prognostic value of cardiac nuclear scintigraphy in patients with preexisting LBBB. The purpose of our study was to determine the prognostic value of cardiac nuclear scintigraphy in patients with preexisting LBBB. METHODS: Ninety-six patients with preexisting LBBB underwent perfusion imaging between July 1987 and June 1995. Thirty-seven underwent planar 201Tl imaging, and 59 underwent SPECT sestamibi imaging. Images were interpreted by consensus of two experienced observers and classified as normal, abnormal low risk and abnormal high risk. Outcomes measured were survival, cardiac and noncardiac death. The final study group included 43 women and 53 men, aged 42-83 (mean 66 +/- 9). Average follow-up was 3.4 +/- 2.1 yr. RESULTS: Of the 96 patients examined, 31 had normal scans, 39 had low-risk scans and 26 had high-risk scans. At the end of the study period, 27 patients with normal scans were still alive while 2 suffered cardiac death and 2 suffered noncardiac death. Of those with low-risk scans, 36 survived while 2 suffered cardiac death and 1 suffered noncardiac death. Finally, of those with high-risk scans, 17 survived while 8 suffered cardiac death and 1 suffered noncardiac death (chi-square test, p = 0.020). CONCLUSION: Dipyridamole imaging is an important prognostic tool for predicting future cardiac events in patients with preexisting LBBB and aids in their risk stratification for coronary artery disease.

Safety and efficacy of monotherapy with fantofarone, a novel calcium channel antagonist, in patients with chronic stable angina pectoris. Fantofarone Study Group.

Fantofarone is a calcium channel antagonist of a class (sulfone indolizine) that is structurally different from the existing classes. The primary cardiac action of fantofarone is on the sinus node, although it is also a potent peripheral and coronary vasodilator. This is a multicenter, double-blind, randomized, placebo-controlled, dose-ranging study evaluating the efficacy and safety of fantofarone. Three hundred and thirty patients were included as intent-to-treat, and 299 patients completed the entire protocol. Doses of fantofarone studied were 50, 100, 150, and 200 mg twice daily. The 100- and 150-mg groups demonstrated antianginal activity, prolonging exercise time walking on a treadmill by 38 and 45 seconds to the endpoint of moderate angina, compared with the placebo group. Sinus bradycardia occurred in 23 patients and was somewhat dose-related. Systolic blood pressure at rest and while exercising was not altered by therapy. No deaths occurred in the treated group. Of the 20 patients in the treatment group who did not complete the protocol (compared with 23 in the placebo group) 6 were dropped because of symptomatic bradycardia, 5 because of increased angina, and 9 for miscellaneous reasons. In doses of 100 mg to 150 mg twice daily, monotherapy fantofarone was effective and safe in the treatment of patients with chronic, stable angina pectoris.

Effects of late percutaneous transluminal coronary angioplasty of an occluded infarct-related coronary artery on left ventricular function in patients with a recent (< 6 weeks) Q-wave acute myocardial infarction (Total Occlusion Post-Myocardial Infarction Intervention Study [TOMIIS]--a pilot study).

The effect of late percutaneous transluminal coronary angioplasty (PTCA) of an occluded infarct-related artery on left ventricular ejection fraction was studied in patients with a recent, first Q-wave myocardial infarction in a prospective, randomized study. Forty-four patients (31 men and 13 women, mean age 58 +/- 12 years) with an occluded infarct-related coronary artery were randomized to PTCA (n = 25) or no PTCA (n = 19). Patients received acetylsalicylic acid, a beta blocker and an angiotensin-converting enzyme inhibitor unless contraindicated. Left ventricular ejection fraction was determined at baseline and 4 months. Coronary angiography was repeated at 4 months. Baseline ejection fraction measured 20 +/- 12 days after myocardial infarction was 45 +/- 12% in both groups. PTCA was performed 21 +/- 13 days after the event. The primary PTCA success rate was 72%. One patient in each group died before angiographic follow-up, which was completed in 37 of the remaining 42 patients (88%; 21 with and 16 without PTCA). At 4 months, the infarct-related artery was patent in 43% of PTCA patients and in 19% of no PTCA patients (p = NS). Reocclusion occurred in 40% of patients after successful PTCA. Secondary analyses showed that the change in left ventricular ejection fraction was significantly greater in patients with a patent infarct-related artery (+9.4 +/- 6.2%) than in those with an occluded artery (+1.6 +/- 8.8%; p = 0.0096). Baseline ejection fraction also independently predicted improvement in left ventricular ejection fraction (p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Safety and clinical utility of combined intravenous dipyridamole/symptom-limited exercise stress test with thallium-201 imaging in patients with known or suspected coronary artery disease.

Dipyridamole-induced coronary hyperemia with 201Tl myocardial perfusion scintigraphy can detect ischemic regions in individuals unable to perform adequate exercise, but it has several limitations. Symptom-limited exercise supplementation to intravenous dipyridamole can potentially overcome them, but the safety and diagnostic accuracy for this combination has not been established. Between 1987 and 1991, 441 consecutive patients were assessed for combined symptom-limited exercise test preceded by i.v. dipyridamole. Clinical records could not be obtained for 37 patients, and 40 patients were not exercised because they were unable; therefore 384 patients (mean age 58 +/- 9.8 yr, 278 men) underwent symptom-limited exercise preceded by 0.56 mg/kg of dipyridamole and followed by planar 201Tl perfusion scintigraphy. Following dipyridamole infusion, systolic blood pressure fell by 10 +/- 14 mmHg and heart rate increased by 8 +/- 11 bpm. Adverse effects were experienced by 77 people (dizziness in 44; headache in 11; nausea in 9; syncope in 2 and chest pain in 11). Exercise heart rate was 69% +/- 16% of predicted maximum and ST shift was -0.9 +/- 0.9 mm. Following exercise, seven patients required aminophylline (four after dizziness, two after headache, one after chest pain), which was uniformly successful. There were no episodes of prolonged chest pain, MI, death or serious arrhythmia. Safety was maintained for people with severe triple coronary artery disease, the elderly (> 70 yr) and those with significant pulmonary disease. Sensitivity was 95% for at least one with > 70% luminal stenosis and 94% for at least one with > 40% luminal stenosis. Specificity was 28% and 53% respectively. The addition of a symptom-limited exercise test to i.v. dipyridamole is safe for all groups of patients referred for 201Tl study.

Contemporary medical management of left ventricular dysfunction and congestive heart failure.

OBJECTIVE: The primary purpose of this review was to address the following question: based on the best available evidence, what should be the current medical management of congestive heart failure (CHF)? DATA SOURCES: The major sources for this review were from searches of the English language literature, including computer and bibliography reviews, of all randomized, controlled clinical trials and overview analyses of positive inotropic agents, preload/afterload reduction agents and beta-blocker medications in CHF. STUDY SELECTION: The number of studies reviewed was approximately 40. The major criterion for selection was that the studies be of CHF patients in randomized controlled clinical trials, particularly with a mortality/survival endpoint. Additional clinical trials of nonmortality endpoints in CHF patients and mortality trials in non-CHF patients were also selected to support possible pathophysiological insights for future CHF trials. DATA EXTRACTION: The data, particularly for the accompanying tables, were initially extracted by a single reviewer using common qualitative guidelines as far as was possible within the different temporal, etiological and geographic frameworks of the original component studies. Conclusions are drawn from this data synthesis and from published overviews. DATA SYNTHESIS: Angiotensin converting enzyme (ACE) inhibition therapy is effective in reducing mortality and morbidity in severe left ventricular dysfunction and CHF. Other systemic vasodilators may also be beneficial. The effects of digitalis on survival and morbidity in CHF are presently uncertain, but should be resolved in the near future. Other inotropic agents, at least in the long term, are clinically detrimental. Diuretics decrease morbidity, but their effect on mortality in CHF remains unknown. Beta-blocker and magnesium therapy offer promise in CHF, but await definitive clinical trials evaluation. CONCLUSIONS: The current medical therapy of CHF should definitely include ACE inhibitors, probably diuretics and possibly other vasodilators. Further viable trials of promising new, and older heretofore under-evaluated, CHF therapies are needed. Additionally, innovative strategies are needed to deal with this disease which has an increasing prevalence. Two strategies, primary prevention of CHF and a 'Heart Function Clinic', are discussed.

Effect of left ventricular unloading with captopril on remodelling and function during healing of anterior transmural myocardial infarction in the dog.

OBJECTIVE: To determine whether left ventricular (LV) unloading with captopril between two days and six weeks during healing after transmural anterior acute myocardial infarction might prevent further LV remodelling and preserve function in the canine model. DESIGN: Serial LV topographic and functional parameters (two-dimensional echocardiograms) and hemodynamics over six weeks and scar topography (planimetry) and collagen (hydroxyproline) at six weeks were measured in 34 chronically instrumented dogs; 24 with anterior transmural acute myocardial infarction (coronary artery ligation and collateral obliteration) that had been randomized at two days post infarction to therapy with oral 50 mg bid placebo (n = 12) or captopril (n = 12) for six weeks, and 10 with sham infarction. MAIN RESULTS: At six weeks, captopril and placebo groups had similar scar mass (7.7 versus 8.1% LV), infarct hydroxyproline and transmurality but the captopril group showed significantly less (P less than or equal to 0.05) infarct expansion and thinning, cavity dilation, epicardial and endocardial bulge. Between two days and six weeks, captopril decreased mean left atrial and arterial pressures compared to placebo or sham. Echocardiograms at two days showed similar LV asynergy, ejection fraction, infarct expansion and thinning with placebo and captopril. In contrast, echocardiograms between two days and six weeks showed that: further expansion and thinning occurred with placebo but not captopril; LV volumes increased with placebo but decreased with captopril; total LV asynergy was unchanged with placebo but decreased with captopril; and LV ejection fraction was unchanged with placebo but increased with captopril. At six weeks, LV ejection fraction was 10% higher (45 versus 35%, P less than 0.001) and LV aneurysm was less frequent (33 versus 100%, P less than 0.005) with captopril compared to placebo. CONCLUSIONS: Chronic LV unloading with captopril therapy during healing after canine transmural anterior acute myocardial infarction limits further remodelling, decreases aneurysm formation and improves function.

Fine structural alterations in radiofrequency energy-induced lesions in dog hearts: possible basis for reduced arrhythmic complications.

OBJECTIVE: To define fine structural changes in canine myocardium due to radiofrequency energy; to compare these changes with those due to direct current shock; and to determine if differences found can explain the reduction in arrhythmic complications observed following the use of radiofrequency energy. ANIMALS: Ten mongrel dogs were used for radiofrequency energy and seven for direct current shock experiments. DESIGN: Twenty-five Joules of direct current and 150 to 300 J of radiofrequency energy were delivered via catheters to the myocardium of anesthetized dogs. The endomyocardium was excised and processed for electron microscopy. MAIN RESULTS: The endomyocardial damage produced by radiofrequency energy and direct current shock was similar at the light microscopic levels. Ultrastructurally, the myocyte changes were similar but the supporting vasculature was better preserved in the direct current-damaged myocardium. CONCLUSION: The lack of vascular preservation in radiofrequency energy-induced damage compared to direct current shock myocardial damage may provide a morphological background for the reduced arrhythmic complications noted.