Ventricular tachyarrhythmias in patients receiving an implantable cardioverter-defibrillator for primary versus secondary prophylaxis indications.

INTRODUCTION: Data on the mechanisms of sudden cardiac death are limited and may be biased by delays in rhythm recording and selection bias in survivors. As a result, the relative contributions of monomorphic ventricular tachycardia (VT) (cycle length [CL] > 260 ms), monomorphic fast VT (FVT) (CL ≤ 260 ms), and polymorphic VT (PMVT)/ventricular fibrillation (VF) have not been well characterized nor compared in patients with and without prior arrhythmic events. METHODS: A retrospective cohort study of implantable cardioverter-defibrillator (ICD) recipients with primary or secondary implant indications was used to evaluate intracardiac electrograms (EGMs) for the first spontaneous VT/VF resulting in appropriate ICD therapy. EGMs were categorized into VT, FVT, and PMVT/VF based on CL and morphologic criteria. RESULTS: Of 616 implants, 145 patients (58 [40%] primary indications) received appropriate ICD therapy for VT/VF over mean follow-up of 3.8 ± 3.2 years. Primary implants had more diabetes (28% vs 12%; P = 0.02) and less antiarrhythmic use (15% vs 33%; P = 0.02). In those patients with spontaneous arrhythmia, PMVT/VF occurred in 20.7% of primary versus 21.8% of secondary implants, FVT in 19.0% versus 21.8%, and VT in 60.3% versus 56.4%, respectively (P = 0.88). Spontaneous VT CL was similar regardless of implant indication (284 ± 56 [primary] vs 286 ± 67 ms [secondary]; P = 0.92). CONCLUSIONS: Monomorphic VT is the most common cause of appropriate ICD therapy regardless of implant indication. These results provide insight into the mechanisms of sudden cardiac death and have implications for the use of interventions designed to limit ICD shocks.

Missed diagnosis of limited ascending aortic dissection by multiple imaging modalities leading to fatal cardiac tamponade and aortic rupture.

Modern diagnostic imaging modalities for ascending aortic dissection include transesophageal echocardiography (TEE), computed tomography angiography (CTA), and magnetic imaging resonance (MRI). All have extremely high sensitivity and specificity for detection of an intimal flap to diagnose ascending aortic dissection. We present a case of fatal cardiac tamponade caused by a limited aortic dissection not detected by multiple imaging modalities. This may represent a class of aortic dissection variant that cannot be detected by conventional testing. A high index of suspicion should be maintained in the appropriate clinical setting and should prompt serial imaging and even consideration for preemptive surgical exploration.

Use of hand carried ultrasound, B-type natriuretic peptide, and clinical assessment in identifying abnormal left ventricular filling pressures in patients referred for right heart catheterization.

BACKGROUND: The estimation of left ventricular filling pressure (LVFP) remains a critical component in the management of patients with known or suspected acute heart failure syndromes. Although right heart catheterization (RHC) remains the gold standard, several noninvasive parameters, including clinical assessment, B-type natriuretic peptides (BNP), and echocardiography can approximate LVFP. We sought to use a combination of these measures to noninvasively predict high or low LVFP in a population referred for RHC. METHODS AND RESULTS: The study consisted of validation of hand-carried ultrasound (HCU)-derived measurement of mitral E/E' against standard echocardiograms in 50 patients, as well as direct comparison of jugular venous pressure (JVP), a clinical congestion score, HCU-derived E/E' and maximum inferior vena cava diameter (IVCmax), and BNP with pulmonary capillary wedge pressure (PCWP) in another 50 patients. The mean age was 61 years, ejection fraction 40%, JVP 9 cm, BNP 948 pg/mL, IVCmax 2.1 cm, E/E' 13, and PCWP 21. All parameters performed well in determining PCWP >or=15 mm Hg, with clinical score performing the worst (area under the receiver-operator characteristic curve [AUC] 0.74), and IVCmax performing the best (AUC 0.89). JVP, in combination with HCU-derived parameters and BNP performed better than any of the individual tests alone (AUC 0.97 for combination of all 3). CONCLUSIONS: Clinical score, JVP, HCU indices, and BNP perform well at identifying patients with a PCWP >or=15 mm Hg. Use of these indices alone or in combination can be used to identify and potentially monitor patients with high LVFP in the inpatient and outpatient settings.

Takotsubo cardiomyopathy induced by dobutamine infusion: a new phenomenon or an old disease with a new name.

Takotsubo cardiomyopathy mimics acute myocardial infarction but is a separate clinical entity characterized by distinct wall motion abnormalities in the absence of obstructive coronary lesions. The prevalence of this condition is relatively uncommon yet has gained increasing recognition in recent years. It has rarely been associated with the use of dobutamine infusion during cardiac stress testing. We present in detail two cases of dobutamine-induced Takotsubo cardiomyopathy from our case series, one from 2002 and the other from 2008. While both cases display the typical features of Takotsubo cardiomyopathy, the former was initially diagnosed as dobutamine-induced vasospasm. These cases may provide insight into the pathophysiological mechanism of the condition and suggest that the increasing recognition of Takotsubo cardiomyopathy results from increasing familiarity of the condition.

Aldosterone receptor blockade in patients with left ventricular systolic dysfunction following acute myocardial infarction.

Left ventricular systolic dysfunction (LVSD) is a common complication of acute myocardial infarction (AMI) that occurs in approximately 30% of post-AMI patients, and results in a threefold increase in in-hospital and 6-month mortality, regardless of type of AMI. Post-AMI care has evolved to include early reperfusion, antiplatelet therapy, hydroxymethylglutaryl coenzyme A reductase inhibitors (stains), beta blockers, angiotentsin-converting enzyme inhibitors, and angiotensin receptor blockers. Despite these therapies, however, there is still an excess of sudden cardiac death (SCD), especially in patients with severe LVSD and in the first 30 days post-AMI. Aldosterone has been shown to be elevated in patients with post-AMI LVSD and to have deleterious effects on the myocardium, including endothelial dysfunction, collagen deposition, inflammation, apoptosis, and autonomic instability, leading to left ventricular remodeling and SCD. Aldosterone blockade with eplerenone has been shown to reduce mortality even in the presence of optimal post-AMI therapy in patients with post-AMI LVSD. Despite this, eplerenone is underutilized in real-world clinical practice. Care must be taken to follow renal function and potassium balance in patients treated with eplerenone.

High prevalence of cardiac autonomic dysfunction and T-wave alternans in dialysis patients.

BACKGROUND: Chronic hemodialysis (HD) patients have an elevated risk of sudden cardiac death (SCD), particularly in the 24 hours before the first HD of the week. Temporal changes in cardiac autonomic dysfunction, as characterized by abnormalities in heart rate variability (HRV) and heart rate turbulence (HRT), along with T-wave alternans (TWA), may contribute to this dispersion of risk. OBJECTIVE: This study sought to determine the prevalence of abnormal HRV, HRT, and TWA in HD patients and to compare their temporal distribution among periods of variable SCD risk. METHODS: HRV, HRT, and TWA were analyzed from 72-hour Holter monitors in HD patients, and results were compared among the 24-hour high-risk period before the first dialysis session of the week, the 24-hour intermediate-risk period beginning with the weeks' first dialysis, and the low-risk period the day after the first dialysis. Positive cut points were standard deviation of all normal R-R intervals ≤70 ms for HRV, onset ≥0% and/or slope ≤2.5 ms/R-R for HRT, and ≥53 µV for TWA. RESULTS: Of 41 enrollees, 28 (46% male, age 55 ± 12, ejection fraction 57% ± 11%) had sufficient data for analysis. Abnormalities were prevalent with 82%, 75%, and 96% of patients reaching threshold for HRV, HRT, and TWA in at least one 24-hour period, respectively. There was no significant difference in the prevalence of abnormal measures among dialytic intervals nor in the intraindividual distribution of abnormal measures (P >.05 for all). CONCLUSION: Abnormal HRV, HRT, and TWA are prevalent in HD patients and may indicate heightened SCD risk. No significant correlation was observed among these measures and recognized periods of variable risk.

Prognostic markers in heart failure--congestion, neurohormones, and the cardiorenal syndrome.

There are several markers of poor prognosis in heart failure (HF). The most established markers of poor prognosis in HF include neurohormonal (NH) imbalance, low ejection fraction (EF), ventricular arrhythmias, intraventricular conduction delays, low functional capacity, low SBP, and renal failure. The relative importance of these factors is unknown, as they have never been studied together. We present a 74-year-old female with nonischemic cardiomyopathy and an EF<20% who over 24 years since diagnosis, never developed clinical or hemodynamic congestion, was never hospitalized for HF, and never required a loop diuretic. She had all of the clinical indicators of poor prognosis in HF except for severe NH imbalance and renal failure, illustrating their importance in HF prognosis. While NH activation in HF is initially an adaptive mechanism, an imbalance of NH effectors causes congestion leading to a vicious cycle of congestion, renal dysfunction, and worsening of HF. The combination of NH activation and renal failure in HF is a vasomotor nephropathy known as the cardiorenal syndrome (CRS) and portends a poor prognosis. Pharmacological disruption of NH pathways early in HF may prevent CRS and, therefore, improve outcomes.