Presence Of Left Ventricular Aneurysm Research Articles

813 The added value of transthoracic three dimensional echocardiography in apical hypertrophic cardiomyopathy

Abstract We present the case of a 73-year-old patient with a recent diagnosis of hypertrophic cardiomyopathy (HCM). He was asymptomatic and has no family history of sudden cardiac death (SCD), syncope or ventricular arrhythmias. An echocardiogram performed at the moment of diagnosis (2020), showed left ventricular (LV) asymmetric apical hypertrophy with maximal wall thickness of 21 mm. Cardiac magnetic resonance (CMR) confirmed LV apical hypertrophy with mid-ventricular obliteration, and late gadolinium enhancement in the apical segments, without wall motion abnormalities present at rest. According to 2014 ESC guidelines, his calculated risk score for sudden cardiac death was low (1.23% at 5 years). On 2021, a comprehensive transthoracic echocardiographic examination including advanced techniques (three-dimensional echo-3DE-, and two-dimensional speckle-tracking-2DSTE) was done as part of his routine follow-up in our cardiomyopathy outpatient clinic. The echo study showed an asymmetric pattern of LV hypertrophy with a maximal wall thickness of 21 mm at the level of the anterolateral apical segment, normal LV volumes (end-diastolic volume 55 mL/m2) and ejection fraction (69%) by 3DE. LV longitudinal strain analysis by 2DSTE showed impaired LV myocardial deformation mainly at the apical LV segments (GLS = −13.6%). There was evidence of dynamic intracavitary obstruction (maximal gradient 32 mmHg at rest and raised to 52 mmHg during Valsalva manoeuvre). 3DE views of the LV (both multi-slice display and 3D rendered image) allowed to avoid foreshortening of the LV apical views, and to appreciate the actual wall motion at the real LV apex. They revealed a LV apical aneurysm which was not detected in the conventional LV-focused apical 2D views (Figure 1A and B). Apical hypertrophic cardiomyopathy (ApHCM) is a variant of HCM that is characteristic of focal thickening of the LV apical myocardium and was reported to have a more benign course than other non-apical forms. However, the presence of LV aneurysm in ApHCM patients is associated with an increased risk for ventricular arrhythmias, sudden cardiac death and thromboembolism. Accordingly, the detection of apical LV aneurysms has significant impact on patient management. Guidelines recommend the use of contrast echocardiography or CMR when the apical region of the LV is suboptimally visualized by conventional 2D echocardiography. However, contrast echocardiography may still be affected by apical foreshortening resulting in suboptimal accuracy, as it is a 2D technique. On the other end, CMR may be contraindicated or not widely available for routine yearly follow-up for all HCM patients requiring regular imaging follow-up. Our clinical case emphasizes the added value of 3DE to increase the sensitivity of transthoracic echocardiography in detecting apical LV aneurysms in patients with apical HCM with important clinical implications for the management of the patient. 813 Figure 1(A) 2D 4chamber-view showing maximal wall thickness in the apical segments (21 mm) with apical obliteration. At a first evaluation, apical aneurism is not easily detected. (B) 4D rendering of the apex showing the apical aneurism.

Predictors and prognosis of left ventricular thrombus in post-myocardial infarction patients with left ventricular dysfunction after percutaneous coronary intervention.

We aimed to investigate the predictors and prognosis of left ventricular thrombus (LVT) in patients admitted for post-myocardial infarction (MI) and left ventricular dysfunction after contemporary percutaneous coronary intervention (PCI). We prospectively enrolled 267 consecutive post-MI patients with left ventricular ejection fraction (LVEF) <0.45 based on the Shanghai East Hospital PCI database since 2012. Altogether 25 (9.36%) patients were selected as the LVT group. Baseline, angiographic, procedural characteristics and 1-year clinical outcomes were compared by Chi-square test, t-test or Kaplan-Meier survival analysis as appropriate. Receiver operating characteristic (ROC) curves were plotted for the accuracy of the multivariate analysis model. A multiple logistic regression was applied to predict LVT formation. The independent risk factors of LVT were left ventricular aneurysm [odds ratio (OR): 1.29, 95% confidence interval (CI): 1.09-1.52, P<0.01], incomplete revascularization (OR: 0.05, 95% CI: 0.01-0.35, P<0.01), SYNTAX score (OR: 1.28, 95% CI: 1.14-1.43, P<0.01) and D-dimer (OR: 1.90, 95% CI: 1.19-3.04, P<0.01). The SYNTAX score and D-dimer effectively indicated the development of LVT with optimal cutoff values of 29.50 and 1.53 mg/L, respectively. Patients with LVT had significantly worse outcomes at 1-year clinical follow-up, especially higher incidence of ischemic or hemorrhagic stroke. This study indicated that the presence of left ventricular aneurysm, incomplete revascularization, higher SYNTAX score and D-dimer level were the independent predictors of LVT formation in post-MI and LV dysfunction patients, which related to worse clinical outcomes. Future studies for early intervention and complete revascularization in high-risk subgroup patients are expected.

Aneurysm-related ischemic ventricular tachycardia: safety and efficacy of catheter ablation.

Left ventricular aneurysm (LVA) postmyocardial infarction (MI) might be an arrhythmogenic substrate. We examined the safety and efficacy of catheter ablation of LVA-related ventricular tachycardia (VT).Thirty-three consecutive patients who underwent primary catheter ablation of ischemic VT were divided into LVA group (11 patients, mean age 61.9 years, 10 men) and none LVA group. Acute procedural outcomes, complications, and long-term outcomes were assessed.In LVA group, average number of induced VTs were 3.2 ± 2.6 (range 1–7), clinical VTs were located in the ventricular septum scar zone in 4 (36.4%) patients, acute success was achieved in 7 (63.6%) patients, partial success in 3 (27.3%) and failure in 1 patient, while none LVA group showing a statistically similar distribution of acute procedural outcomes (P = 0.52). There were no major or life-threatening complications. VT-free survival rate at median 19 (1–44) months follow-up was numerically but not significantly lower in LVA versus none LVA group (48.5% vs 62.8%, log-rank P = 0.40).Catheter ablation of ischemic VT in the presence of LVA appears feasible and effective, with about one-third of cases having septal ablation targets. Further studies are warranted.

Factors Associated With Immediate Results of Coronary Artery Bypass Grafting in Patients With Ischemic Heart Disease in the Presence of Type 2 Diabetes

to elucidate factors associated with cardiovascular events (CVE) after coronary artery bypass grafting (CABG) depending on the presence of type 2 diabetes mellitus (DM2). Medical records of 667 patients who underwent CABG during the period from 2006 to 2009 (317 patients with and 350 patients without DM2 and other disorders of glucose metabolism with comparable by sex, age and CABG characteristics) were analyzed retrospectively. The relationship of registered possible predictors with incidence of CVE was evaluated in a logistic regression model. Predictors of CVE after CABG were different depending on the presence of DM2. The presence of left ventricular aneurysm, mitral regurgitation, reduced left ventricular ejection fraction (LVEF) and elevated level of glycated hemoglobin were independent predictors of CVE in diabetic patients. The increase in the age of patients, on-pump CABG, combined operations, presence of mitral regurgitation, decrease in LVEF were predictors of CVE in non-diabetic patients. Predictors of CVE after CABG were different depending on the presence of DM2. Data obtained emphasize the importance of control of glycaemia in patients with DM2 for improvement of immediate results of CABG.

CORONARY EMBOLISM WITH FRAGMENTED THROMBUS FROM THE LEFT VENTRICLE IN PATIENT WITH POSTINFARCTION ANEURYSM

The thrombus formation in the left ventricle (LV) cavity is a frequent complication of myocardial infarction (MI) as well as a risk factor for peripheral arterial embolism. Probability of intraventricular thrombus depends on MI location and its therapy. A case of coronary embolism in a patient with anterior MI and thrombus in the LV aneurysm is considered in details. Successful percutaneous coronary intervention (PCI) in the first 90 minutes after admission was performed. Decision to appoint a three-component antithrombotic therapy (acetylsalicylic acid, clopidogrel, warfarin) was made on the 4th day of disease onset taking into account the combination of MI, stent placement in the anterior interventricular artery and the presence of left ventricular aneurysm with parietal thrombus. Recurrence of MI developed on the 9th day of disease onset. Aspiration thromboembolectomy was performed taking into account thrombosis of two coronary arteries. Warfarin therapy was discontinued in connection with subsequent clot lysis and development of not intensive nosebleed. Subsequent MI course was uneventful. In conclusion, even in spite of the timely achievement of PCI and early reperfusion, MI course can be complicated by thrombosis of the left ventricle and subsequent development of thromboembolic complications.

Determinants of inducibility of ventricular tachycardia

We analyzed the incidence and predictive factors for induction of clinical ventricular tachycardia (VT) during an electrophysiologic study in 127 patients with structural heart disease and spontaneous VT documented by 12-lead electrocardiography. Eighty-five patients had coronary artery disease (CAD), 24 had idiopathic dilated cardiomyopathy (IDC), and 18 had right ventricular dysplasia (RVD). Clinical variables were age, gender, electrocardiographic patterns of spontaneous arrhythmia, cardiac diagnosis, left ventricular (LV) ejection fraction (EF), infarct location, and presence of LV aneurysm. Clinical VT was induced in 76 patients (60%, group 1) and was not induced in 51 patients (group 2). Clinical VT was induced in 83% of patients with RVD, 58% of patients with CAD, and 50% of patients with IDC (p = 0.07). LVEF tended to be significantly higher in group 1 than in group 2 (p = 0.06). The presence of left QRS axis in the frontal plane during spontaneous VT was significantly associated with a higher inducibility both in the general group (69% vs 46%, p <0.02) and in patients with CAD (70% vs 44%, p <0.02). In patients with CAD, only the presence of a left QRS axis was significantly associated with a higher inducibility. A multivariate analysis identified only the left QRS axis as a significant and independent predictor of induction of clinical VT. The association of a leftward axis with inducibility suggests that vectorial factors in the depolarization wavefronts may be related to inducibility since conventional stimulation is performed from the right ventricle, producing a leftward axis in most cases.

Influence of thrombolytic therapy on the incidence of left ventricular thrombi after acute anterior myocardial infarction: role of successful reperfusion.

Previous studies have reported controversial results regarding the effectiveness of systemic thrombolysis in preventing left ventricular (LV) thrombus after acute myocardial infarction (MI). This study was performed to evaluate the influences of thrombolysis, and particularly successful reperfusion, on the incidence of LV thrombus formation after acute anterior MI. In all, 191 patients suffering from a first attack of acute anterior MI were prospectively evaluated by two-dimensional echocardiography and coronary angiography, performed at the end of the first week and within the first two weeks of MI, respectively. Of these, 98 who presented within 12 h of onset of symptoms received intravenous streptokinase (1.5 million IU), while the remaining 93 patients who, either because of contraindications or late admission, did not receive thrombolytic treatment served as control group. All patients received aspirin and full-dose anticoagulation with intravenous heparin. Successful reperfusion in the streptokinase group was assessed by enzymatic and electrocardiographic evidence. The overall incidence of LV thrombi was 24.6% (47/191). When all patients were evaluated, no statistically significant difference was found between the frequency of LV thrombi in the patients who had thrombolysis (22.4%) and those who did not (26.8%), despite a trend toward the formation of fewer thrombi in the initial group (p > 0.05). However, the patients who had successful reperfusion with streptokinase (n = 64) had significantly reduced incidence of LV thrombi compared with those who did not receive thrombolytic therapy (20 vs. 26.8%, p < 0.05). Stepwise multivariate analysis suggested that LV abnormal wall motion score (p = 0.01) and presence of LV aneurysm were independent predictors of LV thrombus formation in patients with acute anterior MI. Not all patients who received streptokinase for acute anterior MI, but only those with successful reperfusion had reduced incidence of LV thrombi. The favorable effects of thrombolysis on LV thrombus formation are probably due to the preservation of global LV systolic function.

Left Ventricular Size and Function in Patients with Noninsulin-Dependent Diabetes and Postinfarction Total or Subtotal Coronary Occlusions

The aim of this study was to establish the effects of postinfarction total or subtotal coronary occlusion on left ventricular remodeling in patients with noninsulin-dependent diabetes (NIDD) compared with the effects in postinfarct nondiabetic patients. The authors selected 100 patients submitted to coronary angiography between 1 and 5 weeks after acute myocardial infarction (T0: 20.5+/-15.4 days) and classified into three groups: G1: NIDD with coronary occlusion/subocclusion (n=24), G2: controls with coronary occlusion/subocclusion (n=43), G3: controls without coronary occlusion/subocclusion (n=33). At time zero (T0) the following parameters were evaluated: end-systolic and end-diastolic volume indexes (ESVi, EDVi), ejection fraction (EF), echocardiographic wall motion score index (WMI), presence of left ventricular aneurysm, and triple-vessel coronary disease. The frequencies of major cardiovascular events were recorded during follow-up. Significantly greater ESVi and EDVi were noted in G2 compared with G3 (P<0.0001), while no significant differences were observed between NIDD patients and controls. Although left ventricular global and segmental dysfunctions were increased in diabetics, controls with coronary occlusion/subocclusion presented more pronounced EF reduction (P<0.0001 G2 vs G3) and higher elevation in WMI (P<0.005 G2 vs G3). Cardiac events during follow-up were elevated in G1 and G2, particularly as regards the occurrence of congestive heart failure. The authors conclude that NIDD seems to influence in a positive way left ventricular remodeling associated with postinfarct total or subtotal coronary occlusion.

Prognostic significance of left ventricular aneurysm in the Cardiac Arrhythmia Suppression Trial (CAST) population

Left ventricular aneurysm has been associated with increased mortality rates. The Cardiac Arrhythmia Suppression Trial (CAST) database was used prospectively to assess (1) the prognostic significance of left ventricular (LV) aneurysm after myocardial infarction on mortality rates and (2) the relation of LV aneurysm to ventricular arrhythmias and their suppressibility. All patients in the CAST study were enrolled after myocardial infarction. They had ≥6 ventricular premature depolarizations (VPDs) per hour and ejection fraction ≤55%; they were enrolled in the study an average of 96 days after the index myocardial infarction. Of 2494 patients with wall motion data, 164 had LV aneurysm, 600 had only dyskinesis, 913 had only akinesis, and 817 had none of these. Radionuclide scan was used in 39%, two-dimensional echocardiography in 30%, and LV angiogram in 31%. Baseline VPDs and nonsustained ventricular tachycardia were similar in all groups. LV aneurysm patients were more frequently eliminated during open-label titration. The incidence of sustained VT during follow-up was only 2.8% for aneurysm patients, a rate that was similar to the other groups. Patients with LV aneurysm had significantly lower survival rates (82% vs 91%) at 16 months after study entry than those without these wall motion abnormalities ( p < 0.005). When survival rates were adjusted for ejection fraction there was still a moderately large hazard ratio (1.34) of LV aneurysm that was not statistically significant ( p = 0.18). We conclude that (1) the presence of LV aneurysm does not independently worsen prognosis, and (2) older concepts of LV aneurysm and ventricular arrhythmias must be reevaluated.

Selection of patients for programmed ventricular stimulation: A clinical decision-marking model based on multivariate analysis of clinical variables

Objective. This study was conducted to assess the utility of clinical variables in predicting the inducibility of sustained ventricular arrhythmias in a heterogeneous group of patients undergoing programmed ventricular stimulation.Methods. Variables were considered in a simulated chronologic order to determine the incremental information added by the signal-averaged electrocardiogram (ECG) and left ventricular ejection fraction. All patients undergoing baseline programmed ventricular stimulation for induction of ventricular tachyarrhythmia during a 30-month period were included in the study. Fourteen historical, ECG, signal-averaged ECG and left ventricular wall motion variables were evaluated for their ability in predicting inducibility of a sustained ventricular arrhythmia, a “positive” event, at programmed ventricular stimulation.Results. On univariate analysis of the clinical variables, comparison between patients with positive or negative results showed significant differences in 10 of the 14 clinical variables: major cardiac diagnosis, history of ventricular tachycardia, myocardial infarction by history or ECG, all five signal-averaged ECG variables; left ventricular ejection fraction and presence of left ventricular aneurysm. On multivariate analysis, five independent variables were determined to be important: history of ventricular tachycardia, historical or ECG evidence of myocardial infarction, history of loss of consciousness, filtered QRS duration on the signal-averaged ECG and left ventricular ejection fraction. However, with sequential multivariate analysis, a model based only on historical and conventional ECG data was found to do as well as a model that included signal-averaged ECG and left ventricular ejection fraction data.Conclusions. Routinely available noninvasive historical, ECG, signal-averaged ECG and left ventricular wall motion variables can be used to accurately predict the outcome of programmed ventricular stimulation. The majority of the predictive power was obtained with the routine model, using only historical and ECG data. The signal-averaged ECG and left ventricular wall motion analysis added no significant incremental information.

Early and Late Survival After Coronary Artery Surgery

Between 1970 and 1985, 1801 patients underwent coronary-artery surgery without associated valvular surgery. Eighty-four per cent of patients were male and the mean (+/- SD) age was 55.7 +/- 8.3 years. Of the patients, 18.7% were from the Coronary Care Unit and 6.5% had diabetes. The hospital mortality rate for the whole group was 3.5%. Patients from the Coronary Care Unit had the highest (8.9%) hospital mortality rate compared with those patients who were not from the Coronary Care Unit (2.1%; P less than 0.001). Other factors which increased the hospital mortality rate significantly were the number of diseased vessels (P less than 0.01), the degree of left main coronary-artery stenosis (P less than 0.001), an earlier year of surgery (P less than 0.01) and female sex (P less than 0.01). After these were taken into account, no other factors (for example, age, preoperative infarction, presence of left-ventricular aneurysm, left-ventricular end-diastolic pressure, diabetes, use of mammary-arterial grafts or the need for endarterectomy) affected the mortality rate. Patients were followed-up for a mean (+/- SD) of 4.4 +/- 2.8 years. The five-year survival rate for all patients was 88% and the 10-year survival rate was 65%. Cox regression analysis showed that the significant indicators of decreased long-term survival were undergoing operation directly from the Coronary Care Unit (P less than 0.001), left main coronary-artery stenosis (P less than 0.01), the number of grafted vessels (P less than 0.01), concomitant surgery for aneurysm (P less than 0.001), year of surgery (P less than 0.01). Seventy-nine per cent of patients were free of angina pectoris at five years after operation. The year of surgery (P less than 0.001) and preoperative myocardial infarction (P less than 0.05) were the best predictors of recurrent angina. In the long term, recurrent angina remains a problem, although this may change with the increased use of mammary-arterial grafts.

Early and late survival after coronary‐artery surgery

Between 1970 and 1985, 1801 patients underwent coronary-artery surgery without associated valvular surgery. Eighty-four per cent of patients were male and the mean (+/- SD) age was 55.7 +/- 8.3 years. Of the patients, 18.7% were from the Coronary Care Unit and 6.5% had diabetes. The hospital mortality rate for the whole group was 3.5%. Patients from the Coronary Care Unit had the highest (8.9%) hospital mortality rate compared with those patients who were not from the Coronary Care Unit (2.1%; P less than 0.001). Other factors which increased the hospital mortality rate significantly were the number of diseased vessels (P less than 0.01), the degree of left main coronary-artery stenosis (P less than 0.001), an earlier year of surgery (P less than 0.01) and female sex (P less than 0.01). After these were taken into account, no other factors (for example, age, preoperative infarction, presence of left-ventricular aneurysm, left-ventricular end-diastolic pressure, diabetes, use of mammary-arterial grafts or the need for endarterectomy) affected the mortality rate. Patients were followed-up for a mean (+/- SD) of 4.4 +/- 2.8 years. The five-year survival rate for all patients was 88% and the 10-year survival rate was 65%. Cox regression analysis showed that the significant indicators of decreased long-term survival were undergoing operation directly from the Coronary Care Unit (P less than 0.001), left main coronary-artery stenosis (P less than 0.01), the number of grafted vessels (P less than 0.01), concomitant surgery for aneurysm (P less than 0.001), year of surgery (P less than 0.01). Seventy-nine per cent of patients were free of angina pectoris at five years after operation. The year of surgery (P less than 0.001) and preoperative myocardial infarction (P less than 0.05) were the best predictors of recurrent angina. In the long term, recurrent angina remains a problem, although this may change with the increased use of mammary-arterial grafts.

Improved results in the operative management of ventricular tachycardia related to inferior wall infarction: Importance of the annular isthmus

Ventricular tachycardia associated with inferior wall myocardial infarction has had a lower surgical cure rate with localized subendocardial resection than ventricular tachycardia related to anterior infarction. Some investigators have advocated visually directed extensive subendocardial resection, including resection of the papillary muscles and mitral valve replacement, even without documenting the origin of ventricular tachycardia at these sites. We have operated on 46 patients (43 men and three women) for ventricular tachycardia associated with inferior wall myocardial infarction. Thirty-one consecutive patients (Group I) had standard localized subendocardial resection. Two patients in this group had mitral valve replacement for mitral insufficiency. Fifteen consecutive recent patients (Group II) underwent subendocardial resection plus focal endocardial cryoablation (3 minutes at -70 degrees C) of the annular isthmus. The annular isthmus is defined as the ventricular muscle between the basal end of the ventriculotomy and the mitral valve anulus. In Group I there were four operative deaths (13%). Ventricular tachycardia was noninducible in 15 of 27 operative survivors (56%) at postoperative electrophysiologic studies. In Group II there was one operative death (7%) and 13 of 14 survivors (93%) had no inducible ventricular tachycardia at postoperative electrophysiologic studies (p less than 0.01 versus Group I). No Group II patient required mitral valve replacement. Six operative survivors in Group II had intraoperative activation maps consistent with macroreentry incorporating the annular isthmus. Group I and Group II were indistinguishable in terms of preoperative hemodynamics, number of coronary arteries diseased, or the presence of left ventricular aneurysm. These results suggest that subendocardial resection with additional cryoablation of the annular isthmus results in improved control of ventricular tachycardia in patients with ventricular tachycardia associated with inferior wall myocardial infarction. Mitral valve replacement is not required unless intrinsic mitral valve disease is present. These data also suggest that the annular isthmus is a critical component of the reentrant circuit in these tachycardias.

Relation of st-segment elevation after healing of acute myocardial infarction to the presence of left ventricular aneurysm

Persistent ST elevation after healing of myocardial infarction (MI) is often cited as an electrocardiographic sign of left ventrlcular (LV) aneurysm. This sign is rare in patients with coronary artery disease who have normal or only mildly deranged LV function and is most often associated with QRS patterns indicative of large MI, especially anterior wall MI. To determine whether ST elevation identifies a distinctive abnormality of LV function that might be labeled LV aneurysm, global and regional LV function in 12 patients with QRS patterns of anterior MI and ST elevation were compared with that in 12 patients with similar QRS abnormalities but without ST elevation by means of radionuclide ventriculography. All measured parameters of ventricular function were similar in the 2 groups. ST elevation could not be demonstrated to predict a distinctive abnormality that might be labeled LV aneurysm.

Identifying patients at risk of sudden death after myocardial infarction: Value of the response to programmed stimulation, degree of ventricular ectopic activity and severity of left ventricular dysfunction

The ability of programmed ventricular stimulation to identify risk of sudden death after acute myocardial infarction (MI) was compared with 24-hour electrocardiographic assessment of ventricular ectopic activity and determination of left ventricular (LV) dysfunction. Forty-six patients underwent programmed stimulation 8 to 60 days (mean 22) after documented MI. Programmed stimulation consisted of single and double extrastimuli from the right ventricular apex at 2 times diastolic threshold during ventricular pacing and normal sinus rhythm. Of the 46 patients, 44 underwent electrocardiographic monitoring at least 6 days after MI. In 43 of the 46 patients, LV ejection fraction (EF) and the presence of LV aneurysm were determined. In response to programmed ventricular stimulation, 5 patients had sustained ventricular tachycardia (VT), 5 had nonsustained VT (≥4 beats), 13 had intraventricular reentrant repetitive responses, and 23 had either bundle branch reentrant repetitive responses or no extra responses to programmed ventricular stimulation (negative study). During a mean follow-up of 18 months, 10 patients died, 6 suddenly. One of the 10 patients with sustained or nonsustained VT died suddenly, compared with 3 of 13 patients with intraventricular reentrant responses and 2 of 23 patients with a negative study (difference not significant). Of 25 patients with Grade 0 to 2 ventricular ectopic activity, 3 died suddenly after MI, compared with 3 of 19 patients with Grade 3 or 4 activity (difference not significant). By comparison, the frequency of sudden death was greater in patients with an LVEF of <40% (5 of 16 versus 1 of 27 patients) or an LV aneurysm (5 of 13 versus 1 of 30 patients). Thus, using the described protocol, the response to programmed ventricular stimulation is not helpful in identifying patients at risk for sudden death after MI. The presence of an LV aneurysm or EF of <40% appears to provide the greatest prognostic information with respect to risk for sudden cardiac death.