Endocardial Voltage Research Articles

Integration of Three-Dimensional Scar Maps for Ventricular Tachycardia Ablation With Positron Emission Tomography-Computed Tomography

This study sought to assess the feasibility of deriving 3-dimensional (3D) scar maps from positron emission tomography (PET)/computed tomography (CT) hybrid imaging and to integrate those into clinical mapping systems to assist in ventricular tachycardia (VT) ablations. Ablation strategies for nonidiopathic VT are increasingly based on the anatomic information of the scar and its border zone. However, the current "gold standard" of voltage mapping is limited by its inability to accurately describe a complex 3D scar morphology, its imperfect spatial resolution, and prolonged procedure times. Fourteen patients underwent PET/CT multimodality imaging before the VT ablation. We used PET/CT-derived scar maps to characterize myocardial scar using a 17-segment analysis and surface reconstruction. In 10 patients, reconstructed 3D metabolic scar maps were integrated into a clinical mapping system and compared with high-resolution voltage maps. A good correlation was found between the voltage maps and PET/CT-derived scar maps (r = 0.89; r < 0.05). In addition, 3D metabolic scar maps accurately displayed endocardial and epicardial surface and could be successfully integrated with a registration error of 3.7 +/- 0.7 mm. A combination of visual alignment and surface registration was most accurate for myocardial scar accounting for </=15% of the left ventricular surface. Scar size, location, and border zone accurately predicted high-resolution voltage map findings (r = 0.87; p < 0.05). Integrated scar maps revealed metabolically active channels within the myocardial scar not detected by voltage mapping and correctly predicted non-transmural scar despite normal endocardial voltage recordings. Areas of low voltage within wall segments displaying preserved metabolic activity were shown to be due to suboptimal catheter contact and prevented unnecessary ablation lesions. We found that PET/CT fusion imaging is able to accurately assess left ventricular scar and its border zone. The integration of a 3D scar map into a clinical mapping system is feasible and may allow supplementary scar characterization that is not available from voltage maps. This technique could significantly facilitate substrate-based VT ablations.

A Case Study on Cardiac Imaging in Patients with Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy —A Comparison between 64-Slice Computed Tomography, Magnetic Resonance Imaging and Electroanatomical Mapping—

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an uncommon type of cardiomyopathy with fibrofatty tissue replacement. Magnetic resonance imaging (MRI) is a sophisticated method for the diagnosis of ARVD/C. Electroanatomical mapping has been reported to rapidly provide accurate data that facilitates catheter ablation of VT in ARVD/C. In addition, multislice CT (MSCT) is fast, easy to perform, and has a more reliable image quality. MSCT is considered a clinically valuable, noninvasive tool for assessment of myocardial pathology. However, the relationship between MSCT, cardiac MRI and electroanatomical mapping imaging in patients with ARVD/C is unknown. We report two cases diagnosed as ARVD/C by endomyocardial biopsy. In one case MRI imaging revealed marked wall thinning and a decrease in wall motion in the inferior wall and basal interventricular septum of the left ventricle. In another case an electroanatomical map of the RV was created. Endocardial voltage mapping in sinus rhythm revealed a large low voltage area and a focal pattern of activation was documented in activation mapping during VT. In both cases MSCT demonstrated low density areas indicative of focal fatty infiltration and morphological and functional abnormalities which were simultaneously assessed with MRI or electroanatomical mapping.

Abstract 2247: Feasibility of Long Ventricular Transmural Linear Lesions Created with a New Novel Saline-Injection Needle Catheter: Utility for Ablating Scar Related VT

Introduction: Unstable scar related ventricular tachycardia (VT) is a common problem after myocardial infarction. Aggressive ablation may be limited, however, by incomplete scar penetration with available RF energy delivery technologies. The purpose of this study was to test the feasibility of full thickness linear ablation of infarcted ventricular substrate with a high penetration virtual electrode needle based electrode system. Methods: Chronic infarcted (&gt; 2months) mongrel dogs (35–40 kg) underwent percutaneous catheter ablation of the LV with a saline-injection needle catheter employing an 8 mm 20-GA tip. Constant power at 40W was delivered for 90 sec via the virtual electrode needle during infusion of saline 10 ml/h at 50°C. The lines were created under electroanatomic map guidance and intracardiac ultrasound (ICE). The ejection fraction was monitored immediately before and after the ablation. One week after ablation, the dogs where restudied using CARTO epicardial and endocardial voltage mapping and hemodynamic testing. Results: The ablation lines created by a virtual electrode energy delivery made in the antero-lateral wall showed mean length of 4.4±1.4 cm. The mean area of ablation per lesion in the endocardium, mid myocardium and epicardium was 1.1±1.0, 2.6±1.3 and 1.9±1.3 cm 2 (p&lt;0.05) respectively, with a mean ablation depth of 1.5±0.5 cm. Sixty-four percent of the length of lesions were transmural and in non-transmural areas had an average depth of 90±16% of wall thickness. The mean number of gaps/line was 0.5±0.7 with a length of 0.6 cm. Ejection fraction was 50±14, 52±17 and 52±13% before, after and 1 week post ablation respectively. At one week the epicardial and endocardial areas of low bipolar voltage &lt; 1.5mV and dense scar &lt; 0.5mV in the Carto map were 11.4±1.2 and 7.9±6.1cm 2 respectively which measurements were confirmed at necropsy by macroscopic scar in the epicardium and endocardium of 11.8±4.3 and 6.6±4.1 cm 2 respectively. Conclusion: This new novel saline-injection needle catheter effectively creates continuous long transmural lines in the infarcted LV. These data also confirm that the macroscopic ablation lesions can be consistently and accurately monitored by 3D electroanatomical mapping in both endocardium and epicardium.

Catheter Ablation for Ventricular Tachycardia

Sustained ventricular tachycardia (VT) is an important cause of morbidity and sudden death in patients with heart disease.1 Implantable cardioverter-defibrillators (ICDs) terminate VT episodes, reducing the risk of sudden death. Recurrent VT develops in 40% to 60% of patients who receive an ICD after an episode of spontaneous sustained VT. A first episode of VT occurs in ≈20% of patients within 3 to 5 years after ICD implantation for primary prevention of sudden death in high-risk groups.2–4 ICD shocks reduce quality of life and are associated with an increased risk of death.2–4 Antiarrhythmic drug therapy with amiodarone or sotalol reduces VT episodes but with disappointing incidence of side effects and efficacy.2 Catheter ablation is useful for reducing VT episodes and can be life-saving when VT is incessant.1,5,6 Idiopathic VTs occur in patients without structural heart disease and rarely cause sudden death. Electrophysiological study with catheter ablation is often warranted to confirm the diagnosis, to provide further evidence for the absence of ventricular scar or other disease, and often to cure the arrhythmia. Ablation is also an option for symptomatic nonsustained VT and frequent ventricular ectopy in these patients.1 The appearance of the VT on ECG often suggests its likely cause and associated heart disease (Figure 1). Monomorphic VT has the same QRS complex from beat to beat, indicating repetitive ventricular activation from a structural substrate or focus that can be targeted for ablation. Most are due to reentry through regions of ventricular scar.7 Figure 1. ECG types of VT and most common causes are shown with characteristic ECG features of selected VTs. LBBB indicates left bundle-branch block; LVOT, LV outflow tract; RBBB, right bundle-branch block; L, left; and R, right. Polymorphic VTs have a changing ventricular activation sequence that can be due to …

Normal Atrial Activation and Voltage During Sinus Rhythm in the Human Heart: An Endocardial and Epicardial Mapping Study in Patients with a History of Atrial Fibrillation

The three-dimensional contributions to human atrial activation in sinus rhythm have not been specifically characterized. We evaluated the sequence of endocardial and epicardial activation and voltage of the atria during normal sinus rhythm. The study group includes 35 patients with history of symptomatic atrial fibrillation. Prior to catheter ablation of atrial fibrillation, we performed multielectrode electroanatomic mapping during sinus rhythm, endocardially of the RA, LA, and coronary sinus (CS) and, in 10 patients, epicardially of the transverse sinus and oblique sinus. Following activation of the atrial region of the sinus node, the epicardial transverse sinus was activated 11 +/- 18 msec later, while the earliest endocardial LA activation occurred in the region of Bachmann's bundle at 31 +/- 13 msec, significantly earlier than the earliest epicardial LA activation of the oblique sinus at 54 +/- 10 msec (P < 0.002). The posterior LA revealed complex types of activation in 66% of patients analyzed, due to the convergence of wavefront propagation from the CS, oblique sinus, and endocardial LA. Bipolar voltage measurements revealed significantly higher values for the epicardium (mean 3.05 +/- 1.31 mv) than for the endocardium (mean 1.65 +/- 0.75 mv), P < 0.0001 between both groups. In sinus rhythm, we have characterized endocardial and epicardial atrial activation and voltage, and provide an analysis and understanding of the genesis of the P wave complex in humans.

Exercise Electrocardiogram Testing

Exercise testing remains the most widely accessible and relatively inexpensive method for initial evaluation of suspected coronary disease and for evaluation of its severity.1–3 Clinical usefulness has been limited, however, by poor sensitivity of standard ST-segment depression criteria for assessment of anatomic and functional coronary disease severity and for prediction of risk.1,2,4–6 Recent data make it clear that symptomatic obstructive plaques that typically result in exercise-mediated ischemia may be less relevant to infarction and sudden death than less obstructive unstable plaques.7 These limitations mandate a rethinking of the exercise ECG along 2 distinct lines: First, is it possible to improve the diagnostic value of the exercise ECG? Second, separate from its ability to diagnose obstructive coronary artery lesions, can the exercise test be used as a prognostic tool that can encourage effective prevention of premature deaths or coronary events? Both goals take us beyond the ST segment. Reversible ST-segment depression is the characteristic finding associated with exercise-induced, demand-driven ischemia in patients with significant coronary obstruction but no flow limitation at rest. This process differs from the flow-limited acute coronary syndromes because exercise-related ischemia is generally limited to the subendocardium and is proportional to increases in myocardial oxygen demand. Ventricular waveforms of the ECG can be related to the net uncanceled transmural gradients between endocardial and epicardial myocardium, as extrapolated from the work of Holland and Brooks, among others.8–10 Accordingly, isoelectric TQ and ST segments in normal and in nonischemic patients can be related to comparable resting membrane and action potential plateau voltages in endocardial and epicardial action potentials. During exercise, progressive ischemia results in changing endocardial action potentials during both diastole and systole. Less negative endocardial cell resting membrane potential leads to current flow across the ischemic boundary during diastole, leading to elevation of the TQ …

Epicardial Radiofrequency Catheter Ablation of Ventricular Tachycardia in the Vicinity of Coronary Arteries Is Facilitated by Fusion of 3-Dimensional Electroanatomical Mapping With Multislice Computed Tomography

A 65-year-old male patient was referred for radiofrequency catheter ablation of a ventricular tachycardia (VT). The patient had a history of an anterior non–Q-wave infarction. Angiography revealed no significant lesions and normal left ventricular (LV) function. Before ablation, a contrast-enhanced 64-slice computed tomography (CT) scan was acquired. CT data were loaded into an electroanatomical (EA) mapping system (Biosense Webster, Inc, Diamond Bar, Calif) to provide 3-dimensional (3D) CT surface reconstruction of the coronary arteries and LV. Endocardial voltage mapping of the LV was performed during sinus rhythm and the 3D EA mapping data were merged with the 3D surface reconstruction data, allowing real-time visualization of the catheter tip in relation to the surface reconstruction (Figure 1). The clinical VT (cycle length 314 ms) was induced (Figure 2A). Endocardial …

Correlation between endocardial voltage mapping and myocardial perfusion: implications for the assessment of myocardial ischemia

Recent clinical studies using a non-fluoroscopic three-dimensional (3D) left ventricular (LV) mapping system suggested reduced endocardial voltage amplitudes measured in zones sustaining myocardial ischemia or infarction. However, the direct relationship between myocardial perfusion and endomyocardial voltage amplitudes has not been fully elucidated. In a pig model of chronic myocardial ischemia (n = 20), LV endocardial unipolar voltage (UpV) mapping was performed using the Biosense 3D navigation system (Johnson and Johnson, Warren, New Jersey, USA) 4 weeks after ameroid constrictor placement around the left circumflex coronary artery. Echocardiography was used to assess regional changes in myocardial wall thickening (MT) and fluorescent microspheres (4 x 10/injection) were used to quantify rest regional myocardial blood flow (MBF) in ischemic (left circumflex) and remote non-ischemic (left anterior descending) regions. UpV measurements were reduced in ischemic compared to non-ischemic zones (9.9+/-3.3 compared with 13.3+/-3.3 mV, P = 0.03). This corresponded to changes in endocardial MBF and MT, which were both noted to be significantly reduced in the ischemic compared to the non-ischemic area (MBF, 0.50+/-0.16 compared with 0.74+/-0.15 ml/g per min, P = 0.001; MT, 26.1+/-12.0 compared with 37.4+/-10.1%, P=0.003). A positive linear correlation was found between UpV at rest and endomyocardial (but not epicardial) perfusion: UpV (mV) = 7.8+5.9xMBFendocardial (r = 0.32, P = 0.05). Chronic myocardial ischemia, resulting in reduced perfusion and function at rest (that is, hibernating myocardium), is characterized by a significant reduction ( approximately 25%) in endocardial UpV potentials, which correlates with reduced endomyocardial blood flow and tissue perfusion at rest.

Spatial heterogeneity of endocardial voltage amplitude in viable, chronically dysfunctional myocardium.

Although electromechanical mapping has been used to assess cardiac physiology, interpretation is dependent upon the spatial variability of endocardial voltage and local shortening in normal and viable dysfunctional myocardium, which is currently unknown. NOGA mapping was performed in 13 pigs with an established model of viable dysfunctional myocardium produced by a chronic LAD stenosis, and five uninstrumented controls. Voltage maps (122 +/- 7 points each) were obtained in the closed-chest anesthetized state, and (18)F-2-deoxyglucose uptake and TTC staining confirmed viability. There were systematic regional variations in voltage amplitude in both chronically-instrumented and control animals. Unipolar voltage was ~15% higher in LAD-supplied versus remote myocardium (10.8 +/- 0.3 vs. 8.9 +/- 0.4 mV, p < 0.001), with a similar relative difference in controls (14.0 +/- 0.5 vs. 12.0 +/- 0.4 mV, p < 0.02). In contrast, bipolar voltage was ~35% lower in the LAD territory of both groups (2.2 +/- 0.2 vs. 3.5 +/- 0.2 mV, p < 0.01 and 3.1 +/- 0.3 vs. 5.1 +/- 0.3 mV in controls, p < 0.01). The relative dispersion (SD/mean) of voltage was large, but significantly lower for unipolar versus bipolar measurements (39 +/- 1% vs. 70 +/- 2%, p < 0.001). Variability between hearts was partially related to end-systolic volume (r = 0.58, p < 0.05). Linear local shortening measurements were insensitive to detect anterior hypokinesis. Our data demonstrates significant regional and spatial heterogeneity of endocardial voltage and NOGA-derived linear shortening in normal and viable dysfunctional myocardium, with large confidence intervals for individual measurements. Even though the absence of necrosis in this model precludes assessment of the sensitivity and specificity of NOGA mapping to identify infarction, our findings highlight important methodological limitations in using electromechanical mapping to determine viability.

Comparison of endocardial electromechanical mapping with radionuclide perfusion imaging to assess myocardial viability and severity of myocardial ischemia in angina pectoris

The assessment of left ventricular electromechanical activity using a novel, nonfluoroscopic 3-dimensional mapping system demonstrates considerable differences in electrical and mechanical activities within regions of myocardial infarction or ischemia. We sought to determine whether these changes correlate with indexes of myocardial perfusion, viability, or ischemia. A 12-segment comparative analysis was performed in 61 patients (45 men, 61 ± 12 years old) with class III to IV angina, having reversible and/or fixed myocardial perfusion defects on single-photon emission computed tomographic perfusion imaging. A dual-isotope protocol was used, consisting of rest and 4-hour redistribution thallium images followed by adenosine technetium-99m sestamibi imaging. Average rest endocardial unipolar voltage (UpV) and local shortening (LS) mapping values were compared with visually derived perfusion scores. There was gradual and proportional reduction in regional UpV and LS in relation to thallium-201 uptake score at rest (p = 0.0001 and p = 0.0002, respectively) and redistribution studies (p = 0.0001 and p = 0.003, respectively). UpV ≥7.4 mV and LS ≥5.0% had a sensitivity of 78% and 65%, respectively, with a specificity of 68% and 67% for detecting viable myocardium. UpV values of 12.3 and 5.4 mV had 90% specificity and sensitivity, respectively, to predict viable tissue. UpV, but not LS, values differentiated between normal segments and those with adenosine-induced severe perfusion defects (11.8 ± 5.3 vs 8.8 ± 4.1 mV, p = 0.005). Catheter-based left ventricular assessment of electromechanical activity correlates with the degree of single-photon emission computed tomographic perfusion abnormality and can identify myocardial viability with a greater accuracy than myocardial ischemia.

Do Electrode and Lead Design Differences for Permanent Cardiac Pacing Translate into Clinically Demonstrable Differences? (Comparison of Sintered Platinum and Activated Vitreous and Porous Carbon Electrodes)

A randomized prospective study was undertaken to compare the electrical performances of three permanent, endocardial, tined pacing leads with different electrode designs--sintered platinum, vitreous carbon, and porous carbon. Ninety-nine patients received one of the leads (S80 31; 423S 32; S100 36). Acute R wave amplitude and ST elevation of the native endocardial electrogram, voltage threshold, impedance, and current flow at four pulse durations (0.25-1.0 msec) were measured. Voltage thresholds were measured noninvasively at each of four pulse durations at 2 days and 1, 3, and 6 months after implantation. No significant differences were found in sensing properties, or current flow at threshold at 0.5 msec pulse duration. The 423S lead had a significantly higher impedance at threshold and both a higher impedance and lower current flow at 5 V. No significant differences in threshold voltages were found between the three leads at any pulse duration, at any of the assessed times after implantation. Six-month thresholds for the S80, 423S, and S100 leads were 1.18 +/- 0.35, 1.17 +/- 0.29, and 1.06 +/- 0.38 V respectively at 0.5 msec pulse duration. Differences between 'high performance' pacing leads need to be of a greater order of magnitude before they can be exploited to give any real clinical advantage to patients.

Decrease in Canine Endocardial and Epicardial Electrogram Voltages with Exercise: Implications for Pacemaker Sensing

Individuals with permanently implanted pacemakers who have normal sensing and pacing at rest may demonstrate abnormalities, particularly of atrial sensing, with exercise. Exercise is known to cause changes in the surface electrocardiographic voltages. The purpose of this study was to evaluate changes in endocardial and epicardial voltages during exercise in canines with permanently implanted pacing leads similar to those permanently implanted in humans with pacemakers. Six adult mongrel dogs were equipped with transvenous atrial and ventricular endocardial bipolar screw-in leads from a jugular venosection, and with atrial and ventricular bipolar stab-on leads from a left thoracotomy. Exercise was performed at one week following implantation and at weekly intervals for a total of 4 weeks. The animals were studied at rest and at a single workload of 3 miles per hour at a 30% elevation. Unfiltered electrograms were recorded with a VR-12 Electronics-for-Medicine photographic recorder. The mean decreases of electrograms with exercise from resting voltage were: 15% for atrial endocardial unipolar leads; 11% for atrial endocardial bipolar leads; 4% for atrial epicardial unipolar leads; 15% for atrial epicardial bipolar leads; 8% for ventricular endocardial unipolar leads; 18% for ventricular endocardial bipolar leads; 0.1% for ventricular epicardial unipolar leads and 5% for ventricular epicardial bipolar leads.

Endocardial electrogram amplitudes and stimulation thresholds in monopolar electrodes: Possible correlations

The possible correlations between unipolar endocardial electrogram amplitudes and voltage threshold stimulation were tested with electrodes having metallic tips of two different areas. The threshold measurements were always studied with the same pulse characteristics. The data were analyzed through five mathematical functions (linear, exponential, potential, hyperbola and translate hyperbola). The results show a significant correlation, mainly by hyperbolic and exponential functions. Consequently, we could deduce a parameter value since we already knew the other one. This was possible not only during the first implantation, but also later on.