Assessment of ventricular tachycardia scar substrate by intracardiac echocardiography.

BACKGROUND: Intracardiac echocardiography (ICE) is increasingly used to guide complex ablation procedures. This study aimed to assess the scar substrate of ventricular tachycardia (VT) by ICE in patients undergoing VT ablation. METHODS: In 22 patients undergoing VT ablation (10 ischemic, 12 nonischemic), the Biosense CARTOSOUND module (Biosense Webster, Diamond Bar, CA, USA) was used for three-dimensional reconstruction of the ventricles. The characteristics and appearance with ICE imaging of voltage-defined scar zones (bipolar voltage <0.5 mV), border zones (0.5-1.5 mV), and normal myocardium (>1.5 mV) on electroanatomic maps were evaluated. The standard image analysis software Image J (National Institutes of Health, Bethesda, MD, USA) was used to analyze signal intensity (mean pixel signal intensity unit [SIU]) and heterogeneity (standard deviation of signal intensity in analyzed area) on ICE images. RESULTS: A total of 83 myocardial areas were analyzed from two-dimensional ICE images (15 scars, 31 border zones, and 37 normal). Voltage-defined scar zones had increased signal intensities compared to border zones (149 SIU vs 104 SIU, P < 0.0001) and normal myocardium (88 SIU, P < 0.0001). Border zones were more likely to have heterogeneous densities compared to normal myocardium (standard deviation of signal intensity 20 SIU vs 12 SIU, P < 0.0001). In receiver-operator characteristic analyses, signal intensity ≥ 137 SIU differentiated scar from nonscar zones (area under curve 0.91, P < 0.0001). Software-based color enhancement of areas with signal intensity ≥ 137 SIU allowed identification of the VT substrate in all 15 patients with voltage-defined scar zones. CONCLUSIONS: ICE provides important information about the VT anatomical substrate and may have potential to identify areas of scarred myocardium.

Noninvasive assessment of right ventricular function: will there be resurgence in radionuclide imaging techniques?

Right ventricular (RV) function is increasingly being recognized as an important prognostic marker in multiple cardiopulmonary disease states, including congestive heart failure, pulmonary arterial hypertension, and chronic obstructive pulmonary disease. Accurate and reproducible measures of RV function, although technically challenging, are highly relevant in the clinical setting. Radionuclide techniques (eg, first-pass radionuclide angiography for quantifying RV systolic function) were developed nearly 40 years ago. More recently, MRI and transthoracic echocardiography have become the diagnostic imaging techniques of choice for the noninvasive evaluation of RV function. However, developments in single photon emission computed tomography (SPECT), positron emission tomography (PET), and hybrid SPECT/CT and PET/CT systems have greatly improved the image quality and contrast resolution of radionuclide imaging of the heart, allowing for coregistered physiologic and anatomical information of the right ventricle in three dimensions. These improvements in cardiac imaging provide new opportunities for assessing RV myocardial perfusion, function, and anatomy in the same setting. Such imaging approaches may in the future provide assistance with proactive disease management, including early diagnosis of impending RV dysfunction in high-risk patients and for guiding decisions to initiate and/or modify treatments.

Outcome of patients with regadenoson-induced ST-segment depression but normal perfusion on single-photon emission computed tomography.

The prognostic significance of ischemic electrocardiographic (ECG) changes during Regadenoson vasodilator stress in patients with normal single-photon emission computed tomographic myocardial perfusion imaging (SPECT-MPI) is not well described. Of 2473 patients who underwent Regadenoson vasodilator stress testing, 43 (77% women, mean age 72 ± 10 years) patients were included in the study. During a mean follow-up of 14 ± 7 months, cardiac death occurred in 1 patient; 5 patients underwent coronary revascularization and none had myocardial infarction. The annual rate of cardiac death and coronary revascularization was 1.9% and 9.9%, respectively. The finding of ischemic ECG changes with normal SPECT-MPI during regadenoson vasodilator stress testing is uncommon, occurs primarily in older women, and is associated with moderately higher subsequent cardiac event rate.

The Prognostic Significance of Resting Regional Left Ventricular Function in Patients With Varying Degrees of Myocardial Ischemia.

BACKGROUND: Our aim was to determine whether regional left ventricular (LV) function on a resting transthoracic echo (TTE) provides prognostic information in patients with varying degrees of ischemia on myocardial perfusion imaging. METHODS: Between 2004 - 2009, we identified 503 patients (mean age 69 (SD 11); 79% male) with reversible ischemia on a myocardial SPECT scan who had a TTE within 30 days. We evaluated the rate of subsequent revascularization and death for all patients. RESULTS: Following the SPECT scan and TTE, 246/503(49%) patients underwent revascularization, 64/503 (13%) patients died, 369 (73%) patients had a normal left ventricular ejection fraction (LVEF), 242 (48%) patients had a resting wall motion abnormality (WMA), 21/261 (8%) with no WMA died compared to 43/242 (18%) in patients with a WMA. In patients with a WMA (n = 242) there was no significant difference in mortality when comparing patients with small (< 6 segments) and large (> 6 segments) WMA (P = 0.44). In patients with moderate/severe ischemia, the presence of a resting WMA was associated with a higher mortality rate (18% v 7%; P = 0.005). In a multivariable model, LVEF (< 50%) was associated with a hazard ratio of 2.2 (P = 0.002, 95% CI 1.34 - 3.68) however, WMA and number of abnormal segments did not reach statistical significance. CONCLUSION: A resting wall motion abnormality in patients with moderate/severe ischemia is associated with a higher mortality compared to patients with mild ischemia on myocardial perfusion imaging. Regional left ventricular dysfunction unlike LVEF was not an independent predictor of mortality.

4-[18F]-tetraphenylphosphonium as a PET tracer for myocardial mitochondrial membrane potential.

OBJECTIVES: This study tested the hypothesis that 4-[(18)F]fluorophenyltriphenylphosphonium ((18)F-TPP) is useful for in vivo positron emission tomography (PET) measurement of mitochondrial membrane potential (ΔΨm). Its utility as a blood flow tracer also was evaluated. BACKGROUND: Tetraphenylphosphonium is useful for in vitro measurement of ΔΨm. In vivo measurement of ΔΨm has potential value in the assessment of heart failure pathophysiology and therapy as well as assessment of myocardial viability and so may be a very useful clinical tool. METHODS: Anesthetized swine (N = 6) with a balloon catheter in the left anterior descending coronary artery were studied. Microsphere measurements of myocardial blood flow (MBF) were made after balloon inflation (baseline) and ∼10 min after intravenous administration of adenosine and phenylephrine after which ∼10 mCi (18)F-TPP was injected intravenously and dynamic PET data acquisition obtained for 30 min. After the swine were killed, the hearts were sectioned for microsphere measurement of MBF and (18)F-TPP measured by well counter in these same samples. PET images provided whole blood and myocardial (18)F-TPP concentration for determination of ΔΨm by the Nernst equation, corrected for nonspecific (18)F-TPP binding. Microsphere MBF, absolute (ml/min/g) and relative, was compared with PET data (standard uptake value and K1). RESULTS: Nonspecific binding of (18)F-TPP overestimated ΔΨm measured by -37 ± 4 mV (mean ± SD). Normal zone ΔΨm of ex vivo samples (-91 ± 11 mV; N = 52; sample weight, 1.07 ± 0.18 g) correlated strongly (R(2)= 0.93) with normal zone by PET (-81 ± 13 mV). Both ex vivo and PET normal zone ΔΨm, although somewhat lower, compared well with that reported for tritium labeled triphenylphosphonium in normal working Langendorff rat heart (-100 mV). Although the relative MBF by (18)F-TPP correlated strongly with relative microsphere MBF (R(2)= 0.83), there was no correlation between absolute MBF by (18)F-TPP and microsphere MBF. CONCLUSIONS: (18)F-TPP is a promising tracer for noninvasive PET measurement of ΔΨm in living subjects. It is useful as well for assessment of relative but not absolute MBF.

Comparison of dual-source 64-slice adenosine stress CT perfusion with stress-gated SPECT-MPI for evaluation of left ventricular function and volumes.

BACKGROUND: Evaluation of left ventricular (LV) volumes and ejection fraction (LVEF) represent important components of pharmacologic stress imaging with either myocardial CT perfusion (CTP) or gated single-photon emission CT (SPECT) myocardial perfusion imaging (SPECT-MPI). OBJECTIVES: We compared measurements of left ventricular function and volumes obtained with CTP and SPECT-MPI. METHODS: Forty-seven patients (mean age, 62 ± 11 years; male, n = 39) underwent stress CTP and SPECT-MPI. LVEF (in %), end-systolic volume (ESV; in mL), and end-diastolic volume (EDV; in mL) derived from stress CTP images were compared with SPECT-MPI. RESULTS: Stress CTP was in good agreement with SPECT-MPI for quantification of LVEF (r = 0.91), EDV (r = 0.75), and ESV (r = 0.83; all P < 0.001). The mean LVEF measured by stress CTP (66% ± 17%) was similar to SPECT-MPI (64% ± 15%). Similar values were also derived for mean EDV (123 ± 30 mL vs 120 ± 34 mL) and ESV (44 ± 28 mL vs 51 ± 34 mL) for CTP and SPECT-MPI, respectively. Good agreement was also shown between both techniques for the assessment of regional wall motion with identical wall motion scores in 95.3% of the segments (κ = 0.79). CONCLUSIONS: LVEF and LV volume parameters as determined by dual-source 64-slice adenosine stress CTP show a high correlation with values obtained with stress-gated SPECT-MPI.

Emerging Role of Fluorodeoxyglucose-PET in the Diagnosis of Cardiac Sarcoidosis.

Some studies have reported that cardiac sarcoidosis may be responsible for 13% to 25% deaths in patients with systemic sarcoidosis. In the United States the lifetime risk of sarcoidosis is estimated to be 2.4% in blacks and 0.85% in whites. This risk is higher outside the United States, with high incidence in Scandinavia, Ireland, and Japan. Cardiac involvement is more common in the Japanese population, especially in older women. This article discusses the role of cardiac images in the diagnosis of cardiac sarcoidosis, with an emphasis on cardiac fluorodeoxyglucose positron emission tomography.

Usefulness of acute delirium as a predictor of adverse outcomes in patients >65 years of age with acute decompensated heart failure.

Delirium is an acute confusional state that is very prevalent in older patients hospitalized with acute decompensated heart failure (ADHF). The association between delirium and ADHF outcome has not been well described. We analyzed 883 consecutive patients >65 years of age admitted with ADHF. Acute delirium was diagnosed based on the Confusion Assessment Method. Delirious patients (total n = 151) had an increased in-hospital all-cause death compared to nondelirious patients (n = 17, 11%, vs n = 45, 6%; adjusted odds ratio [OR] 1.93, 95% confidence interval [CI] 1.07 to 3.48, p = 0.02). Of those surviving to discharge (n = 821), on multivariable logistic regression analysis, delirium was independently associated with increased risk of 30-day (adjusted OR 4.24, 95% CI 2.77 to 6.47, p <0.001) and 90-day (adjusted OR 3.72, 95% CI 2.51 to 5.54, p <0.001) rehospitalizations for ADHF and higher nursing home placement (adjusted OR 2.70, 95% CI 1.59 to 5.30, p <0.001) after adjusting for age, gender, cardiac risk factors, dementia, activities of daily living, instrumental activities of daily living, coronary artery disease, atrial fibrillation, left ventricular ejection fraction, angiotensin-converting enzyme inhibitor and/or angiotensin receptor blocker, ß blockers, Charlson co-morbidity index, and other potential confounders. Furthermore, delirium was strongly associated with 90-day all-cause mortality in patients discharged from the hospital (adjusted hazard ratio 2.10, CI 1.53 to 2.88, p <0.0001). In conclusion, acute delirium serves as an important prognostic determinant of in-hospital and posthospital discharge outcomes including increased ADHF readmission risk in older hospitalized patients with ADHF. Thus, delirium plays an important role in the risk stratification and prognosis of patients with ADHF.

Exercise-induced ST-segment elevation in ECG lead aVR is a useful indicator of significant left main or ostial LAD coronary artery stenosis.

OBJECTIVES: The authors tested the hypothesis that exercise treadmill testing (ETT)-induced ST-segment elevation (STE) in electrocardiographic lead aVR is an important indicator of significant left main coronary artery (LMCA) or ostial left anterior descending coronary artery (LAD) stenosis. BACKGROUND: Although STE in lead aVR is an indicator of LMCA or very proximal LAD occlusion in acute coronary syndromes, its predictive power in the setting of ETT is uncertain. METHODS: Rest and stress electrocardiograms, clinical and stress test parameters, and single photon-emission computed tomographic myocardial perfusion imaging (MPI) data, when available, were obtained in 454 subjects (378 with MPI) who underwent cardiac catheterization and standard Bruce ETT ≤ 6 months before catheterization. Patients were selected for LMCA or ostial LAD disease (≥ 50% stenosis) with or without other coronary artery disease (CAD), CAD (≥ 70% stenosis) without significant LMCA or ostial LAD, or no significant CAD. Univariate followed by multivariate logistic regression analyses of clinical, electrocardiographic, stress test, and single photon-emission computed tomographic MPI variables were used to identify significant correlates of LMCA or ostial LAD stenosis. Bayesian analysis of the data also was performed. RESULTS: LMCA (n = 38) or ostial LAD (n = 42) stenosis occurred in 75 patients (5 patients had both). The remainder had CAD without LMCA or ostial LAD stenosis (n = 276) or no CAD (n = 103). In multivariate analysis, the strongest predictor was stress-induced STE in lead aVR (p < 0.0001, area under the curve 0.82). Both left ventricular ejection fraction (after stress) and percent reversible LAD ischemia on single photon-emission computed tomographic MPI also contributed significantly in multivariate analysis (p < 0.005 and p < 0.05, respectively, areas under the curve 0.60 and 0.64, respectively). Although additional electrocardiographic, stress test, and MPI variables were significant univariate predictors, none was statistically significant in multivariate analysis. At 1-mm STE in lead aVR, sensitivity for LMCA or ostial LAD stenosis was 75%, specificity was 81%, overall predictive accuracy was 80%, and post-test probability increased nearly 3 times from 17% to 45%. CONCLUSIONS: Stress (ETT)-induced STE in lead aVR is an important indicator of significant LMCA or ostial LAD stenosis and should not be ignored.