Are classic predictors of voltage valid in cardiac amyloidosis? A contemporary analysis of electrocardiographic findings

BACKGROUND

Low voltage electrocardiography (ECG) coupled with increased ventricular wall thickness is the hallmark of cardiac amyloidosis. However, patient characteristics influencing voltage in the general population, including bundle branch block, have not been evaluated in amyloid heart disease.

METHODS

A retrospective analysis was performed of patients with newly diagnosed cardiac amyloidosis from 2002 to 2014. ECG voltage was calculated using limb (sum of QRS complex in leads I, II and III) and precordial (Sokolow: S in V1 plus R in V5-V6) criteria. The associations between voltage and clinical variables were tested using multivariable linear regression. A Cox model assessed the association of voltage with mortality.

RESULTS

In 389 subjects (transthyretin ATTR 186, light chain AL 203), 30% had conduction delay (QRS >120ms). In those with narrow QRS, 68% met low limb, 72% low Sokolow and 57% both criteria, with lower voltages found in AL vs ATTR. LV mass index as well as other typical factors that impact voltage (age, sex, race, hypertension, BSA, and smoking) in the general population were not associated with voltage in this cardiac amyloidosis cohort. Patients with LBBB and IVCD had similar voltages when compared to those with narrow QRS. Voltage was significantly associated with mortality (p<0.001 for both criteria) after multivariable adjustment.

CONCLUSION

Classic predictors of ECG voltage in the general population are not valid in cardiac amyloidosis. In this cohort, the prevalence estimates of ventricular conduction delay and low voltage are higher than previously reported. Voltage predicts mortality after multivariable adjustment.

Subtype-Specific Interactions and Prognosis in Cardiac Amyloidosis

Background

Light chain (AL) and transthyretin (ATTR) amyloidosis have a similar effect on myocardial function but very different disease trajectories and survival. However, limited data are available evaluating subtype‐specific predictors of outcomes in a large contemporary cohort.

Methods and Results

We retrospectively investigated 360 patients at the time of initial diagnosis of cardiac amyloidosis (191 AL and 169 ATTR) from 2002 to 2014. Clinical, laboratory, electrical, and morphologic covariates were evaluated based upon amyloid subtype. ATTR etiology was associated with older age, more chronic medical conditions, and the use of standard heart failure medical therapy. Left ventricular mass index and electrocardiographic voltage were higher in ATTR, while there was no difference in ejection fraction or markers of diastology between subtypes. A multivariable Cox model was generated using previously identified predictors of negative outcomes in cardiac amyloidosis and analyzed after stratification for subsequent amyloid‐specific treatment. An AL etiology was the most predictive variable (hazard ratio 3.143, P<0.001) of 3‐year all‐cause mortality. The only covariate that showed a significantly greater magnitude of effect on mortality in 1 amyloid subtype versus the other was amyloid‐specific treatment in AL (P=0.015). The magnitude of effect of other variables on mortality did not significantly differ between subtypes.

Conclusions

Clinical, morphological, electrical, and biomarker data do not significantly interact with amyloid subtype in its association with mortality, despite the fact that the prognosis in each subtype differs greatly. This suggests an additional factor or factors (such as light chain toxicity) contributing to poorer outcomes in AL amyloid.

Predicting Risk Versus Predicting Potential Survival Benefit Using 123I-mIBG Imaging in Patients With Systolic Dysfunction Eligible for Implantable Cardiac Defibrillator Implantation: Analysis of Data From the Prospective ADMIRE-HF Study

BACKGROUND

Cardiac (123)I-metaiodobenzylguanidine ((123)I-mIBG) imaging improves prognostication in patients with left ventricular (LV) dysfunction. Whether (123)I-mIBG can identify optimal candidates for implantable cardiac defibrillator (ICD) placement is unclear. We examined whether (123)I-mIBG enhances risk assessment and identifies patients with enhanced survival with ICD in a patient cohort with reduced LV function who were candidates for ICD implantation.

METHODS AND RESULTS

We identified 777 patients (66 sites, 12 countries) without ICD at the time of enrollment in Adreview Myocardial Imaging for Risk Evaluation in Heart Failure (ADMIRE-HF) and index (123)I-mIBG study. Patients completed prescribed study protocol and follow-up. Heart-to-mediastinum (H/M) ratio was determined from (123)I-mIBG results. Survival modeling used a Cox proportional hazards mixed-effects model, including a propensity score, to adjust for nonrandomized ICD implantation after (123)I-mIBG. All-cause death occurred in 75 patients (9.6%), and 196 (25%) patients had ICD implantation on follow-up. After adjusting for multiple factors, although the H/M ratio added incremental prognostic value and enhanced reclassification, neither H/M results, BNP levels, nor left ventricular ejection fraction interacted with ICD use in the survival model, indicating that these variables did not identify patients with enhanced survival with ICD implantation. Nonetheless, H/M results did identify the number of lives saved by ICD use per 100 treated.

CONCLUSIONS

We found that although (123)I-mIBG imaging enhances the risk stratification of patients with left ventricular dysfunction who are ICD candidates, it does not identify which patients may have improved survival with ICD placement. However, (123)I-mIBG identifies the absolute benefit gained with ICD use, thus may play a role in optimizing the cost-effectiveness of this intervention.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00126425 and NCT00126438.

Abstract 208: Impact of Symptoms and Degree of Valvular Regurgitation on Patient-perceived Health Status in Patients With Aortic Regurgitation

Background: Patients (pts) with severe aortic regurgitation (AI) often present with symptoms of shortness of breath (SOB) or heart failure (HF); however, the effect of these symptoms and severity of aortic regurgitation on patient-perceived health status is unknown.

Methods: Kansas City Cardiomyopathy Questionnaire (KCCQ) data were collected using tablet computers from pts presenting for routine outpatient cardiovascular assessment between 6/1/2011 and 8/31/2012 who also underwent echocardiography within 90 days. Pts with other valvular lesions (including aortic stenosis) moderate or greater in severity, congenital heart disease, hypertrophic cardiomyopathy, pericarditis or constriction, cardiac amyloid, sarcoid, restrictive cardiomyopathy, or pulmonary hypertension were excluded. Demographic, clinical, historical, and echocardiographic data was collected as per routine. Multiple linear regression was used to assess the association of this information and valve lesion severity with KCCQ summary score (SS).

Results: 590 pts [age 61.9±13.8 years, 363 (61.5%) men, 132 (22%) with prior aortic valve surgery] were identified; 452 with mild, 86 with moderate and 52 with severe AI. Mean KCCQ SS was 74.5±23.7; 74.3±23.0 with mild AI, 73.8±26.2 with moderate AI, and 76.7±19.4 with severe AI (p=NS). SOB was present in 290 pts (49%, KCCQ SS 65.3±23.7), HF in 43 (7.3%, KCCQ SS 50.1±22.3) and both in 36 pts (KCCQ SS 47.0±21.7). After adjusting for multiple factors, linear regression (r2=0.28, p<0.001) revealed that the presence of SOB (β: -13.841, p<0.001) and heart failure (β:-19.484, p<0.001) were associated with lower SS; however, the degree of AI and history of aortic valve surgery were not associated with KCCQ SS. Male sex (β: 7.279, p=0.001), heart rate (β: -0.223, p=0.005), prior CAD (β: -4.364, p=0.038) and BMI (β:-0.357, p=0.035) were also significant in this model. Pt age, presence of atrial fibrillation, angina, hypertension, diabetes, prior CAD, renal disease, cancer, cerebrovascular disease, peripheral vascular disease, left ventricular diastolic dimension and ejection fraction were not significant predictors.

Conclusions: In stable outpatients with AI, KCCQ scores correlate with the presence of shortness of breath and heart failure symptoms, but are not affected by the degree of AI or history of aortic valve surgery. Symptoms rather than diagnosis drives patient perceived health status.

The Heart Failure Overweight/Obesity Survival Paradox: The Missing Sex Link

OBJECTIVES

This study sought to determine whether body mass index (BMI) has a differential impact on survival for females versus males with advanced systolic heart failure (HF).

BACKGROUND

Females have a survival advantage in HF, the mechanisms of which are unclear. There is also a proposed "obesity survival paradox" in which excess adiposity promotes HF survival.

METHODS

We reviewed 3,811 patients with left ventricular ejection fraction ≤40% who had undergone cardiopulmonary exercise testing between 1995 and 2011. The endpoint was all-cause mortality. Multivariable analysis was performed using a Cox proportional hazards model. Because of the nonlinearity of BMI, a restricted cubic spline was used. An interaction term was added to investigate the impact of BMI on mortality by sex.

RESULTS

The unadjusted data demonstrated an overall obesity survival paradox in HF. This survival paradox disappeared for males after adjustment for potential confounders, with overweight and obese males showing higher adjusted mortality hazard ratios compared with normal weight males. Conversely, females in the overweight BMI range (25.0 to 29.9 kg/m(2)) had the lowest adjusted mortality (hazard ratio: 0.84; 95% confidence interval: 0.77 to 0.93; p = 0.0005 compared with normal weight females) with a nadir in mortality hazard just below BMI 30 kg/m(2). The multivariable model supported a differential impact of BMI on mortality in males versus females (p for interaction <0.0001).

CONCLUSIONS

In this advanced HF cohort, an unadjusted obesity survival paradox disappeared after adjustment for confounders. Overweight and obese males had higher adjusted mortality than normal weight males, whereas a BMI in the overweight range was associated with a significant survival benefit in females.

Comparative definitions for moderate-severe ischemia in stress nuclear, echocardiography, and magnetic resonance imaging

The lack of standardized reporting of the magnitude of ischemia on noninvasive imaging contributes to variability in translating the severity of ischemia across stress imaging modalities. We identified the risk of coronary artery disease (CAD) death or myocardial infarction (MI) associated with ≥10% ischemic myocardium on stress nuclear imaging as the risk threshold for stress echocardiography and cardiac magnetic resonance. A narrative review revealed that ≥10% ischemic myocardium on stress nuclear imaging was associated with a median rate of CAD death or MI of 4.9%/year (interquartile range: 3.75% to 5.3%). For stress echocardiography, ≥3 newly dysfunctional segments portend a median rate of CAD death or MI of 4.5%/year (interquartile range: 3.8% to 5.9%). Although imprecisely delineated, moderate-severe ischemia on cardiac magnetic resonance may be indicated by ≥4 of 32 stress perfusion defects or ≥3 dobutamine-induced dysfunctional segments. Risk-based thresholds can define equivalent amounts of ischemia across the stress imaging modalities, which will help to translate a common understanding of patient risk on which to guide subsequent management decisions.

Clinical decision making with myocardial perfusion imaging in patients with known or suspected coronary artery disease

Myocardial perfusion imaging (MPI) to diagnose coronary artery disease (CAD) is best performed in patients with intermediate pretest likelihood of disease; unfortunately, pretest likelihood is often overestimated, resulting in the inappropriate use of perfusion imaging. A good functional capacity often predicts low risk, and MPI for diagnosing CAD should be reserved for individuals with poor exercise capacity, abnormal resting electrocardiography, or an intermediate or high probability of CAD. With respect to anatomy-based testing, coronary CT angiography has a good negative predictive value, but stenosis severity correlates poorly with ischemia. Therefore decision making with respect to revascularization may be limited when a purely noninvasive anatomical test is used. Regarding perfusion imaging, the diagnostic accuracies of SPECT, PET, and cardiac magnetic resonance are similar, though fewer studies are available with cardiac magnetic resonance. PET coronary flow reserve may offer a negative predictive value sufficiently high to exclude severe CAD such that patients with mild to moderate reversible perfusion defects can forego invasive angiography. In addition, combined anatomical and perfusion-based imaging may eventually offer a definitive evaluation for diagnosing CAD, even in higher risk patients. Any remarkable findings on single-photon emission computed tomography and PET MPI studies are valuable for prognostication. Furthermore, assessment of myocardial blood flow with PET is particularly powerful for prognostication as it reflects the end result of many processes that lead to atherosclerosis. Decision making with respect to revascularization is limited for cardiac MRI and PET MPI. In contrast, retrospective radionuclide studies have identified an ischemic threshold, but randomized trials are needed. In patients with at least moderately reduced left ventricular systolic function, viable myocardium as assessed by PET or MRI, appears to identify patients who benefit from revascularization, but well-executed randomized trials are lacking.

Global coronary flow reserve is associated with adverse cardiovascular events independently of luminal angiographic severity and modifies the effect of early revascularization

BACKGROUND

Coronary flow reserve (CFR), an integrated measure of focal, diffuse, and small-vessel coronary artery disease (CAD), identifies patients at risk for cardiac death. We sought to determine the association between CFR, angiographic CAD, and cardiovascular outcomes.

METHODS AND RESULTS

Consecutive patients (n=329) referred for invasive coronary angiography after stress testing with myocardial perfusion positron emission tomography were followed (median 3.1 years) for cardiovascular death and heart failure admission. The extent and severity of angiographic disease were estimated with the use of the CAD prognostic index, and CFR was measured noninvasively by positron emission tomography. A modest inverse correlation was seen between CFR and CAD prognostic index (r=-0.26; P<0.0001). After adjustment for clinical risk score, ejection fraction, global ischemia, and early revascularization, CFR and CAD prognostic index were independently associated with events (hazard ratio for unit decrease in CFR, 2.02; 95% confidence interval, 1.20-3.40; P=0.008; hazard ratio for 10-U increase in CAD prognostic index, 1.17; 95% confidence interval, 1.01-1.34; P=0.032). Subjects with low CFR experienced rates of events similar to those of subjects with high angiographic scores, and those with low CFR or high CAD prognostic index showed the highest risk of events (P=0.001). There was a significant interaction (P=0.039) between CFR and early revascularization by coronary artery bypass grafting, such that patients with low CFR who underwent coronary artery bypass grafting, but not percutaneous coronary intervention, experienced event rates comparable to those with preserved CFR, independently of revascularization.

CONCLUSIONS

CFR was associated with outcomes independently of angiographic CAD and modified the effect of early revascularization. Diffuse atherosclerosis and associated microvascular dysfunction may contribute to the pathophysiology of cardiovascular death and heart failure, and impact the outcomes of revascularization.

Ischemic burden by 3-dimensional myocardial perfusion cardiovascular magnetic resonance: comparison with myocardial perfusion scintigraphy

BACKGROUND

The extent and severity of ischemia on myocardial perfusion scintigraphy (MPS) is commonly used to risk-stratify patients with coronary artery disease. Estimation of ischemic burden by cardiovascular magnetic resonance (CMR) with conventional 2-dimensional myocardial perfusion methods is limited by incomplete cardiac coverage. More recently developed 3-dimensional (3D) myocardial perfusion CMR, however, provides whole-heart coverage. The aim of this study was to compare ischemic burden on 3D myocardial perfusion CMR with (99m)Tc-tetrofosmin MPS.

METHODS AND RESULTS

Forty-five patients who had undergone clinically indicated MPS underwent rest and adenosine stress 3D myocardial perfusion and late gadolinium enhancement CMR. Summed stress and rest scores were calculated for MPS and CMR using a 17-segment model and expressed as a percentage of the maximal possible score. Ischemic burden was defined as the difference between stress and rest scores. 3D myocardial perfusion CMR and MPS agreed in 38 of the 45 patients for the detection of any inducible ischemia. The mean ischemic burden for MPS and CMR was similar (7.5±8.9% versus 6.8±9.5%, respectively, P=0.82) with a strong correlation between techniques (rs=0.70, P<0.001). In a subset of 33 patients who underwent clinically indicated invasive coronary angiography, sensitivities and specificities of the 2 techniques to detect angiographic coronary artery disease were similar (McNemar P=0.45).

CONCLUSIONS

3D myocardial perfusion CMR is an alternative to MPS for detecting the presence and rating the severity of ischemia.

Clinical outcomes in fulminant myocarditis requiring extracorporeal membrane oxygenation: a weighted meta-analysis of 170 patients

BACKGROUND

Fulminant myocarditis (FM) is often a self-resolving entity if the patient survives the acute illness. Venoarterial extracorporeal membrane oxygenation (ECMO) has been used successfully for treatment of cardiogenic shock or cardiac arrest due to FM. However, clinical outcomes are not well understood, in part because of small study sizes. In the absence of large clinical trials, performance of pooled analysis represents the best method for ascertaining survival rates for ECMO.

METHODS

A systematic Medline search was conducted on ECMO for the treatment of FM, updated up to November 2012. Studies with n ≥10 published in the year 2000 or later that reported survival to hospital discharge for FM requiring ECMO were included. Studies that reported only on pediatric patients were excluded. The smaller of studies with overlapping patients were excluded. Cochran Q and I(2) were calculated and reported.

RESULTS

Six studies were included in the analysis, encompassing 170 patients. The minimum and maximum reported rates of survival to hospital discharge were 60.0% and 87.5%, respectively. The cumulative rate was 115/170. The calculated Cochran Q value was 3.63, which was not significant for heterogeneity. The I(2) value was 0%. The pooled estimate rate was 66.9% with a 95% confidence interval of 59.4%-73.7%.

CONCLUSION

More than two-thirds of patients with FM and either cardiogenic shock and/or cardiac arrest survive to hospital discharge with ECMO. These findings could be used in the risk-benefit analysis when initiation of a cardiopulmonary bypass system is being considered for FM.

Assessing the prognostic implications of myocardial perfusion studies: identification of patients at risk vs patients who may benefit from intervention?

Stress myocardial perfusion imaging (MPI) has a well-established role in improving risk stratification. Recent analyses, compared with older data, suggest that the yield of stress MPI has decreased. In part, this trend relates to testing patients with heterogeneous, but improved, risk factor modification. In this setting, positron emission tomography with myocardial flow reserve enhances risk stratification as it reflects the end result of atherosclerosis. Recent studies have also emphasized the clinical impact of incremental risk stratification by assessing net reclassification improvement (NRI). Previous retrospective studies have favored an ischemic threshold to select patients that benefit from revascularization, but this finding has not been corroborated in randomized trials. However, no large randomized trial has directly tested a strategy of revascularization for patients with at least a moderate amount of ischemia at risk. Unfortunately, even when faced with a significantly abnormal MPI result, subsequent action is too often absent.