Endocardial mapping during sinus rhythm in patients with coronary artery disease and nonsustained ventricular tachycardia

[Magnetcardiographic detection of abnormal intraventricular activation in patients with ischemic heart disease with and without tachycardia]

Fragmented and delayed activation of ventricular myocardium can cause malignant tachyarrhythmias. By detection of ventricular late potentials only a severely delayed depolarisation is registered, but not the intra QRS-activation. The aim of this study was to examine the complete phase of ventricular depolarisation, to detect and to quantify abnormal electrical activation by magnetocardiography and to estimate in a small group of patients with coronary heart disease the prognostic significance.In 26 healthy subjects, 32 patients after myocardial infarction without malignant ventricular arrhythmias and 10 patients with coronary heart disease and a history of sustained, monomorph ventricular tachycardia magnetocardiography was performed in a magnetically shielded room. To quantify the fragmentation of QRS a fragmentation-index (FI) was calculated. Besides signal averaged ECG, in patients with coronary heart disease cardiac catheterisation and in patients with arrhythmias electrophysiological testing was performed. The FI for the three groups was significantly different (p<0,005). The mean FI in the group of healthy subjects was 20,4+/-5,4, in the group of postinfarction-patients without arrhythmias 27+/-12,1 and in the group of patients with coronary heart disease and ventricular arrhythmias 49,5+/-17,9. Dichotomized at 36 the sensitivity was 80%, the specifity 93%, the positive predictive value was 66% and the negative predictive value 96%. The FI was correlated to the extent of regional wall-motion-irregularity and global ejection fraction.Analyzing late potentials, the values for sensitivity and positive predictive value were surprisingly low (20% and 50%, respectively). The specifity was 96%, the negative predictive value was 88%. Calculating the FI on the basis of electrical signals only an insufficient discrimination of the groups was possible.In the follow-up period of two years one post-infarctional patient was resusciated because of ventricular fibrillation. The FI of this patient was 17.One patient with coronary 3-vessel-disease and left ventricular ejection fraction of 50% died due to acute myocardial infarction, his FI was 39.

CONCLUSION

By means of magnetocardiography fragmented ventricular activation in patients with coronary heart disease was demonstrated even within the QRS-complex and could be correlated to ventricular tachyarrhythmias.

Magnetocardiographic mapping of QRS fragmentation in patients with a history of malignant tachyarrhythmias

BACKGROUND

The identification of patients at increased risk for ventricular tachycardia or ventricular fibrillation (VT/VF) and sudden cardiac death has consequences for therapeutic options and thus may reduce mortality in patients with coronary artery disease (CAD).

HYPOTHESIS

We hypothesized that the intra-QRS fragmentation in magnetocardiographic recordings is increased in patients with CAD and with a history of VT/VF.

METHODS

Multichannel magnetocardiography (MCG) was carried out in 34 healthy controls, 42 patients with CAD without a history of VT/VF, and 43 patients with CAD and with a history of VT/VF. The intra-QRS fragmentation was quantified by a new fragmentation score. Its spatial distribution was investigated using two-dimensional (2-D) contour maps according to the sensor position of the 49-channel magnetogradiometer.

RESULTS

Patients with CAD and with a history of VT/VF had significantly increased QRS fragmentation compared with patients with CAD without VT/VF or controls (72.9+/-37.5, 48.5+/-14.3, and 42.5+/-7.8, respectively: p <0.05). The area of high fragmentation in 2-D contour maps was twice as large in patients with than in those without a history of VT/VF (represented by the number of MCG channels with high fragmentation: 26.3+/-15.5 vs. 12.4+/-9.9, p<0.0001). Patients prone to VT/VF could be identified with a sensitivity of 64% and a specificity of 90%.

CONCLUSION

In patients with CAD and with a history of VT/VF, intra-QRS fragmentation is increased and the area of high fragmentation in 2-D contour maps is enlarged. These findings may be helpful in identifying patients with CAD at risk for malignant tachyarrhythmias.

Electrophysiological and arrhythmogenic effects of intramyocardial bone marrow cell injection in patients with chronic ischemic heart disease

BACKGROUND

Bone marrow cell injection has been introduced to treat patients with ischemic heart disease. However, focal application of bone marrow cells may generate an arrhythmogenic substrate.

OBJECTIVES

To assess the electrophysiological and arrhythmogenic effects of intramyocardial bone marrow cell injection in patients with chronic myocardial ischemia.

METHODS

Bone marrow was aspirated in 20 patients (65+/-11 years, 19 male) with drug-refractory angina and myocardial ischemia. Electroanatomical mapping (NOGA, Biosense-Webster, Waterloo, Belgium) was performed during mononuclear cell isolation. Areas for cell injection were selected based on the localization of ischemia on SPECT. These areas were mapped in detail to evaluate local bipolar electrogram duration, amplitude and fragmentation. Mononuclear cells were injected in the ischemic area with the NOGA system. SPECT and electroanatomical mapping were repeated at 3 months. Holter monitoring was repeated at 3 and 6 months.

RESULTS

SPECT revealed a decrease in the number of segments with ischemia (3.5+/-2.5 vs. 1.1+/-1.0 at 3 months; P<0.01) and an increased left ventricular ejection fraction (44+/-13% vs. 49+/-17% at 3 months; P=0.02). The number of ventricular premature beats remained unchanged (10+/-24x10(2)/24h vs. 8+/-23x10(2)/24h at 3 months (P=NS) and 12+/-30x10(2)/24h at 6 months (P=NS)). At 3 months follow-up, bone marrow cell injection did not prolong electrogram duration (15.9+/-4.6 ms vs. 15.6+/-4.0 ms; P=NS), decrease electrogram amplitude (3.8+/-1.5 mV vs. 3.8+/-1.5 mV; P=NS), or increase fragmentation (2.0+/-0.5 vs. 1.9+/-0.4; P=NS).

CONCLUSION

Intramyocardial bone marrow cell injection does not increase the incidence of ventricular arrhythmias and does not alter the electrophysiological properties of the injected myocardium.

Human histopathology of electroanatomic mapping after cooled-tip radiofrequency ablation to treat ventricular tachycardia in remote myocardial infarction

INTRODUCTION

Catheter ablation of ventricular tachycardia (VT) in remote myocardial infarction (MI) often requires excessive mapping procedures. Documentation of the electrical substrate via electrogram amplitude may help to identify regions of altered myocardium resembling exit areas of reentrant VTs.

METHODS AND RESULTS

A patient with multiple symptomatic monomorphic VTs (biventricular ICD, remote MI) underwent electroanatomic substrate mapping (CARTOtrade mark) for VT ablation. Regions of scar (bipolar electrogram amplitudes <or=0.5 mV), normal myocardium (>or=1.5 mV), and "altered" myocardium (0.5-1.5 mV) were identified. Ablation was directed to regions with "altered" myocardium based on pace map correlation. After ablation the clinical VT did not reoccur. The patient died due to worsening of heart failure 7 days afterward. During postmortal evaluation specified sites of electroanatomic mapping were correlated to histopathological findings. Annotated scar areas were documented to consist of areas with massive fibrosis (>or=80% of mural composition). Ablations were found to span through regions with intermediate fibrosis (21-79%) mapped as "altered" myocardium. Ablation produced transmural coagulation necrosis of mesh-like fibrotic tissue with interspersed remnants of myocardial cells up to a maximum depth of 7.0 mm. Subendocardial intramural bleedings were universal findings 7 days after ablation.

CONCLUSIONS

Electroanatomic substrate mapping for VT ablation sufficiently identified regions of scar and normal myocardium. Regions with bipolar electrogram amplitudes between 0.5 and 1.5 mV were found to correlate to areas of "intermediate" fibrosis (21-79%) with only remnant strands of myocardial cells and were identified as target region for ablation. Cooled-tip endocardial radiofrequency ablation lead to transmural coagulation necrosis up to a depth of 7.0 mm.

Substrate-modification using electroanatomical mapping in sinus rhythm to treat ventricular tachycardia in patients with ischemic cardiomyopathy

The treatment especially of frequent ischemic VT remains a challenge for medical and catheter ablation procedures. We evaluated the efficacy of a substrate-based procedure to eliminate clinical VTs in this patient collective.

METHODS

In 25 consecutive patients (ejection fraction 37+/-12%) with frequent symptomatic medically refractory ischemic VT (with recurrent ICD-shocks), left ventricular anatomic scar mapping (Biosense Webster CARTO) was performed in order to modify the underlying myocardial substrate. Scar tissue was identified as having bipolar voltages <0.5 mV. Prior to the procedure an electrophysiological study (EPS) to determine number and morphology of inducible VTs was performed. Linear ablation procedures (8 mm tip, 70 Watts, 70 degrees C) were based on the findings of scar areas and proximity to anatomic obstacles. Correct location of ablation was documented by similarity of the morphology during pace-mapping. Follow-up included clinical evaluation, ICD holter interrogation plus holter ECG recording.

RESULTS

The clinical VT was eliminated by linear catheter ablation in 23/25 patients (92%) (failure due to unstable catheter position during transaortic approach in 1 and epicardial origin of VT in 1). In 16/23 patients (70%) complete success could be produced with no VT inducible after substrate modification (1.7+/-1.0 lines per patient). In 7 patients (30%) only partial success was documented with further VTs inducible after ablation. No procedure-related complications occurred. During follow- up (10+/-4 months) 4 patients (16%) had occurrences of new VTs documented on ICD holter (3 patients with initially partial success and 1 with initial complete success) differing in cycle length and morphology from the clinical VT. Comparing patients with complete to those with partial success, there was a statistically significant difference of 93 vs. 48% freedom of arrhythmia (p=0.03). No difference in regard to baseline characteristics existed in these two patient subgroups.

CONCLUSIONS

Ablation of frequent VTs in patients with ischemic cardiomyopathy can be safely performed using electro-anatomic scar mapping with a high procedural success of 90%. Based on the morphological findings, linear ablation can suppress inducibility of all VTs in 70% of patients with high mid-term efficacy. In patients with only partial ablation success, non-clinical VTs often occur early during follow-up (50%).

Magnetocardiographic analysis of the two-dimensional distribution of intra-QRS fractionated activation

The spatial distribution of high-frequency components in magnetic signals during the QRS complex of the human heartbeat was investigated. Cardiomagnetic signals were recorded simultaneously using 49 first-order magnetogradiometer channels of a multi-SQUID system with a low noise power density. The QRS fragmentation score S, as a measure of the fragmentation of the bandpass-filtered QRS complex, was examined for its sensitivity and specificity to discriminate 34 healthy volunteers, 42 post-myocardial infarction patients and 43 patients with coronary heart disease and with a history of malignant sustained ventricular tachycardia or ventricular fibrillation. The multichannel information was visualized by two-dimensional mapping of the score values of the single channels. By averaging the score values for the seven central channels, S7, the score values of all 49 channels, S49, and calculating the standard deviation for all 49 channels, D49, a higher sensitivity and specificity for detecting patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) was reached than by analysis of a single channel. Combination of these parameters furnishes a sensitivity of 90% and a specificity of 70% for identifying patients prone to VT/VF. The results were compared with diagnostic information obtained from the QRS duration of the signal as well as with results obtained by modified QRS integral mapping.

Characteristics of sinus rhythm electrograms at sites of ablation of ventricular tachycardia relative to all other sites: a noncontact mapping study of the entire left ventricle

INTRODUCTION

Regions of the diseased ventricle that activate abnormally during sinus rhythm (SR) may be the areas of slow and disorganized conduction that form the diastolic pathway through which reentry may occur during ventricular tachycardia (VT).

METHODS AND RESULTS

We examined features of electrograms recorded during SR that might indicate a site suitable for ablation of VT using a noncontact mapping system, which enables reconstruction of > 3,000 electrograms. Preablation SR electrogram characteristics at sites of successful radiofrequency ablation (RFA) were examined in 13 patients with 53 VTs. Timing of onset, lateness of activity, electrogram duration, and number of baseline crossing events of reconstructed electrograms at the sites of successful RFA were compared with the electrograms of latest onset, latest activity, longest duration, and most baseline crossing events of all ventricular sites. Onset of activation at sites of successful RFA were 26.9+/-25.2 msec (mean +/- SD) earlier than (and 2.9+/-1.7 cm away from) the site of latest onset of SR activation. Electrogram duration at sites of successful RFA was 83%+/-14.6% of (and 4.3+/-1.8 cm away from) the longest electrogram. The baseline crossing events at sites of successful RFA were 53%+/-22% of (and 4.9+/-1.9 cm away from) the most fractionated electrogram. The latest activity at sites of successful RFA was 21.6+/-24.8 msec earlier than (and 4.3+/-1.6 cm away from) the site of latest activity.

CONCLUSION

Although the site of latest onset of endocardial activation during SR proved to be the most sensitive indicator, the characteristics of SR electrograms did not usefully predict successful ablation sites.

The top ten fallacies of nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) continues to remain a subject of controversy. This is true despite a wealth of epidemiologic and basic/clinical laboratory findings that have accumulated during the past 2 decades. However, these data not only generate the impetus to conduct further research, but also provide compelling arguments against continued adherence to time honored precepts about NSVT that evolved since the inception of the "PVC Hypothesis," although never substantiated by rigorous scientific inquiry. This paper discusses the "top ten" fallacies of NSVT and details the data that support abandonment of them.