Circulation: Clinical Summaries
Original Research Put Into Perspective for the Practicing Clinician
- Cardiovascular Risk of High- Versus Moderate-Intensity Aerobic Exercise in Coronary Heart Disease Patients
- Myocardial Relaxation, Restoring Forces, and Early-Diastolic Load Are Independent Determinants of Left Ventricular Untwisting Rate
- Aortic Regurgitation Quantification Using Cardiovascular Magnetic Resonance: Association With Clinical Outcome
- Echocardiographic Predictors of Outcome in Eisenmenger Syndrome
- Parental Electrocardiographic Screening Identifies a High Degree of Inheritance for Congenital and Childhood Nonimmune Isolated Atrioventricular Block
- A Pilot Study Examining the Severity and Outcome of the Post–Cardiac Arrest Syndrome: A Comparative Analysis of Two Geographically Distinct Hospitals
- Targeting Mannose-Binding Lectin Confers Long-Lasting Protection With a Surprisingly Wide Therapeutic Window in Cerebral Ischemia
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Cardiovascular Risk of High- Versus Moderate-Intensity Aerobic Exercise in Coronary Heart Disease Patients
High level of physical fitness and regular exercise are closely related to cardiovascular health and reduced risk of cardiovascular disease and mortality. Aerobic exercise is therefore strongly recommended for patients with coronary heart disease. Exercise performed at higher relative intensities has been found to elicit greater increase in aerobic capacity and greater cardioprotective effects than exercise at moderate intensities. Despite that higher levels of physical activity are found to reduce cardiovascular events, it is advocated that vigorous activity could also acutely and transiently increase the risk of sudden cardiac events in susceptible persons. We therefore studied the risk of cardiovascular events during organized high-intensity interval exercise training and moderate-intensity training among 4846 coronary heart disease patients in 4 Norwegian cardiac rehabilitation centers. The event rate after patients were exposed to both types of exercise training was low. In a total of 175 820 exercise training hours where all patient performed both types of training, we found 1 fatal cardiac arrest during moderate-intensity exercise (129 456 exercise hours) and 2 nonfatal cardiac arrests during high-intensity interval exercise (46 364 exercise hours). There were no myocardial infarctions in the data material. Because the number of high-intensity training hours was 36% of the number of moderate-intensity hours, the rates of complications to the number of patient-exercise hours were 1 per 129 456 of moderate-intensity exercise and 1 per 23 182 of high-intensity exercise. We believe that our study provides needed knowledge about the risk of high-intensity exercise training for patients undergoing secondary cardiac rehabilitation. See p 1436.
Myocardial Relaxation, Restoring Forces, and Early-Diastolic Load Are Independent Determinants of Left Ventricular Untwisting Rate
Measurement of the left ventricular (LV) untwisting rate (UTR) by speckle tracking echocardiography represents a means to evaluate diastolic function, and UTR has been proposed as a marker of the rate of LV relaxation. The present experimental study confirmed the relationship between peak UTR and rate of LV relaxation. In addition, restoring forces generated by systolic contraction, analogous to the elastic recoil after release of a compressed spring, was another important independent determinant of peak UTR. Furthermore, the present study indicated that early-diastolic load, measured as LV pressure at the onset of filling, is an important and independent determinant of peak UTR. Therefore, in the assessment of LV relaxation rate by measurement of peak UTR, one needs to take into account LV diastolic pressure and the magnitude of restoring forces, as well. Clinically, early-diastolic load would approximate LV end-diastolic pressure, and restoring forces may be reflected in end-systolic volume. The demonstration that restoring forces and early-diastolic load are independent determinants of peak untwisting rate, in addition to the rate of relaxation, may have an impact on how measurements of untwisting rate are interpreted in a clinical context. LV untwisting occurs during LV relaxation and early filling and is therefore a feature of diastole. However, because restoring forces are generated by systolic contraction, changes in peak UTR may also be attributed to changes in contractility. Therefore, it may not be appropriate to conclude that a change in peak UTR reflects a true change in diastolic function. See p 1441.
Aortic Regurgitation Quantification Using Cardiovascular Magnetic Resonance: Association With Clinical Outcome
Timing surgery in patients with significant aortic regurgitation (AR) can be difficult. Currently, surgery is advised for severe regurgitation once symptoms, excess left ventricular (LV) dilation or dysfunction, occur. However, prognosis is already reduced by this stage, and earlier identification of patients suitable for surgery might be beneficial. Accurate quantification of the regurgitation may help, but is difficult with echocardiography. Cardiovascular magnetic resonance can accurately quantify AR and also provides highly accurate measurements of LV volume, but the clinical utility of this has not been established. Our study examined whether quantification of AR and LV volumes with cardiovascular magnetic resonance was associated with the future development of symptoms or other indications for surgery in an initially asymptomatic group with moderate to severe AR. We showed that both severity of AR and LV volumes had significant associations with outcome over the subsequent few years. AR quantification showed a stronger association than LV end-diastolic volume, but the combination of these 2 parameters was better still. Cardiovascular magnetic resonance measurements of AR and LV volumes might enable the identification of potential candidates for early surgery, and this should be tested in a large-scale clinical trial. See p 1452.
Echocardiographic Predictors of Outcome in Eisenmenger Syndrome
Although echocardiography provides accurate information on cardiac anatomy and physiology, as well as prognosis data in patients with idiopathic pulmonary arterial hypertension, only few data exist on the prognostic power of echocardiographic parameters in adults with Eisenmenger syndrome, which was the subject of this study. Our data from a single center on a large contemporary cohort of adults with Eisenmenger syndrome showed that echocardiographic indices of right ventricular function (tricuspid annular plane systolic excursion, ratio of right ventricular effective systolic to diastolic duration) and right atrial area are predictive of mortality, assessed either alone or even more so in a composite score. Because the assessment of functional class remains difficult, especially in patients with congenital heart disease, we believe that this score may be used in the risk stratification of Eisenmenger patients and could influence the decision to initiate or escalate therapy. See p 1461.
Parental Electrocardiographic Screening Identifies a High Degree of Inheritance for Congenital and Childhood Nonimmune Isolated Atrioventricular Block
The origin of congenital or childhood nonimmune isolated atrioventricular (AV) block remains unknown. Because familial clustering of progressive cardiac conduction defects of unknown causes, including congenital AV block, has been reported, we hypothesized that idiopathic AV block in the young may be a heritable disease. This hypothesis was tested in a nationwide (France) retrospective cohort of 141 idiopathic pediatric AV blocks. Screening ECGs from 130 parents (mean age 42.0±6.8 years, 57 couples) were compared with 130 matched healthy control subjects. Although a family history of sudden death or progressive cardiac conduction defect, respectively, was found in only 1.4% and 11.1% of parents, conduction abnormalities were more frequent in parents than in control subjects, found in 50.8% versus 4.6%, respectively (P<0.001), and estimated heritability for isolated conduction disturbances was 91% (standard error, 1.019; P=2.10−16). SCN5A mutation screening identified 2 mutations in 2 patients among 97 children. Thus, ECG screening in parents of children affected by idiopathic AV block revealed diffuse subclinical impairment of cardiac conduction, which provides strong evidence for a genetic origin in congenital and childhood nonimmune isolated AV block. Such an ECG screening may be helpful in clinical practice if other obvious causes have been ruled out. Heritability estimate confirmed a high contribution of genetic factors, which opens the field to further molecular studies. See p 1469.
A Pilot Study Examining the Severity and Outcome of the Post–Cardiac Arrest Syndrome: A Comparative Analysis of Two Geographically Distinct Hospitals
The American Heart Association has suggested that improvements in cardiac arrest outcomes might be driven by grading hospitals on in-hospital mortality rates. By comparing out-of-hospital cardiac arrest patients in Boston and in Detroit, this pilot study explores whether outcomes are heavily influenced by prearrest and intra-arrest conditions independent of hospital care. This study suggests that the severity of a postarrest syndrome is largely reflective of prearrest and intra-arrest conditions. This has implications for any plan to grade hospitals on outcomes from cardiac arrest if such grades would be based on crude mortality rates. See p 1478.
Targeting Mannose-Binding Lectin Confers Long-Lasting Protection With a Surprisingly Wide Therapeutic Window in Cerebral Ischemia
Despite recent substantial progress in prevention and supportive care, stroke is still a leading cause of death and permanent disability worldwide. To date, thrombolysis with tissue plasminogen activator is the only available treatment and its narrow therapeutic window (3–4.5 hours) is one of the main obstacles to finding eligible patients. Thus, new approaches with a wider window of efficacy are needed. This study documents the pivotal role of mannose-binding lectin (MBL), a circulating protein that acts as the first step in activation of the lectin complement pathway in brain ischemic injury. The data show that MBL deposition on the ischemic endothelium represents a key pathogenetic event in brain damage. Importantly, strategies aimed at inhibiting MBL lead to neuroprotection with a time window of efficacy up to 24 to 30 hours postinjury, an extremely important factor in the attempt to translate experimental results into the clinical setting. Detailed analysis of the MBL gene in humans has revealed that a surprisingly high percentage of individuals (15%–30% depending on the population considered) carries a genetic deficiency in MBL that leads to low circulating levels of MBL. Notably, this deficiency is associated with a better outcome after acute stroke in humans. Our data, providing a mechanistic insight into the role of MBL in brain ischemia and the demonstration that its inhibition is protective, strongly support the concept of MBL as a relevant therapeutic target in humans, one with a wide therapeutic window of application. Thus, we propose MBL as a novel therapeutic target for stroke. See p 1484.
- © 2012 American Heart Association, Inc.
- Echocardiographic Predictors of Outcome in Eisenmenger Syndrome
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