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.