Treatment of ventricular tachycardia induced cardiogenic shock by percoronary chemical ablation

Catheter Ablation of Ventricular Tachycardia by Intramyocardial Injection of Ethanol in an Animal Model of Chronic Myocardial Infarction

INTRODUCTION

Direct injection of ethanol into myocardium has been shown to create large, well-demarcated lesions with transmural necrosis in normal ventricular myocardium and in regions of healed myocardial infarction. The aim of this study was to investigate the effects of direct ethanol injection on the inducibility of ventricular tachycardia (VT) in an animal model of chronic myocardial infarction.

METHODS AND RESULTS

Eight sheep with reproducibly inducible VT underwent an electrophysiologic study 139 +/- 65 days after myocardial infarction. Noncontact mapping was used to analyze induced VT. Fifteen different VTs were targeted for catheter ablation. Ablation was achieved by catheter-based intramyocardial injection of a mixture of 96% ethanol, glycerine, and iopromide (ratio 3:1:1). Direct intramyocardial ethanol injection resulted in noninducibility of any VT 20 minutes after ablation in 7 of 8 animals. Four of 5 animals with initially successful ablation remained noninducible for any VT at follow-up study at least 2 days after the ablation procedure. Microscopic examination revealed homogeneous lesions with interstitial edema, intramural hemorrhage, and myofibrillar degeneration at the lesion border. The lesions were well demarcated from the surrounding tissue by a border zone of neutrophilic infiltration.

CONCLUSION

Catheter ablation of VT by direct intramyocardial injection of ethanol during the chronic phase of myocardial infarction is feasible. It may be a useful tool for catheter ablation when the area of interest is located deep intramyocardially or subepicardially or when a more regional approach requires ablation of larger amounts of tissue.

Retrograde coronary venous infusion of ethanol for ablation of canine ventricular myocardium

INTRODUCTION

Permanent cure of reentrant ventricular tachycardia (VT) associated with coronary artery disease is difficult to achieve. Retrograde coronary venous infusion of ethanol for ablation of ventricular myocardium associated with reentrant tachyarrhythmias has several potential advantages, including use of physiologic mapping techniques and production of deeper, wider necrotic zones.

METHODS AND RESULTS

Nine anesthetized dogs had baseline hemodynamic measurement, left ventriculography, coronary arteriography, occlusive coronary venography, and programmed electrical stimulation of the right ventricular apex and outflow tract. A balloon-tipped infusion catheter was advanced into a distal coronary venous branch, the balloon slowly inflated, and pure ethanol infused at volumes of 1.5, 3, or 5 cc. Hemodynamic measurements, angiography, ventriculography, and programmed electrical stimulation were repeated immediately and 1 week following ablation. Formalin-perfused hearts were serially sectioned and lesion volumes determined. Histologic examination of ablation beds then was performed. No significant difference was found in any hemodynamic measurement before or after ablation. Coronary arteriograms and left ventriculograms were unchanged after ablation. Nonsustained VT occurred in eight dogs during ethanol infusion; however, VT was not inducible in any dog before or after ablation. Infusion volumes of 3 cc or more were required to produce transmural lesions.

CONCLUSION

Retrograde coronary venous infusions of ethanol using a balloon-tipped infusion catheter were effective in ablating ventricular myocardium. Retrograde chemical ablation did not itself result in inducible VT or adversely affect hemodynamic measurements or coronary arteries. Transmural myocardial necrosis, necessary in the ablation of VT associated with coronary artery disease, can be produced by higher infusion volumes.

The effects of pacing site on left ventricular epicardial surface velocity patterns during systole

Changes in epicardial LV velocity patterns during isovolumic contraction and ejection as induced by ventricular pacing were studied in 15 canines. A noninvasive imaging technique that provided high temporal resolution was used to study the timing of an outward expansion of the LV during isovolumic contraction and the propagation pattern of an inward LV velocity wavefront during ejection. With this technique, surface displacements were measured (+/- 0.1 mm SD) at 50-70 locations on the LV free wall at 5-msec intervals. Velocities were calculated by differentiating the surface displacement waveforms and an interpolation procedure was used to provide detailed color coded velocity maps of the LV surface. LV surface velocities were determined from data obtained during closed-chest endocardial pacing from each of four sites: right atrium, right ventricular apex, left ventricular apex, and right ventricular outflow tract. These surface velocities showed a distinct spatial and temporal pattern for each pacing site. The results show that this noninvasive mapping procedure has potential for determining the location of an ectopic ventricular focus.

Intracoronary ethanol ablation in swine: characterization of myocardial injury in target and remote vascular beds

INTRODUCTION

Physical or chemical ablation of arrhythmogenic tissue has been shown to be an effective modality of arrhythmia therapy. Chemical ablation by intracoronary infusion of ethanol into a specific coronary artery bed has been demonstrated, but the characteristics and distribution of necrosis relative to the coronary blood supply have not been delineated.

METHODS AND RESULTS

A total of 40 myocardial lesions were created in 21 pigs by infusion of 1.6 +/- 0.6 mL of 50% ethanol and 50% iohexol contrast solution through a 2.7 French infusion catheter advanced into a branch of the left anterior descending or circumflex coronary artery. Prior to ethanol infusion, 5.3 +/- 1.2 mCi technetium-99m (Tc-99m) methoxyisobutyl isonitrile (sestamibi) was infused into the coronary branch in order to delineate the perfusion bed. After completion of the lesions, each heart was removed, sliced transversely in 5-mm slices, and stained with nitro blue tetrazolium in order to define the ablation bed. The slices were then imaged with a gamma camera and the area of Tc-99m sestamibi uptake was defined as the perfusion bed. These respective areas were planimetered for each slice and compared. No difference was observed in hemodynamic parameters between preablation and postablation measures except mean arterial pressure, which fell from 122 +/- 22 mmHg to 116 +/- 24 mmHg (P = 0.02). Significant ventricular arrhythmias were observed after 60% of the ablations. The mean left ventricular ejection fraction fell from 55% +/- 9% to 45% +/- 15% after completion of all ablations. The areas of the ablation beds were related to the areas of the perfusion beds but the correlation was poor (r = 0.41, P = 0.0001). Generally, the ablation bed was smaller than the perfusion bed, but evidence of ethanol reflux was observed in 29% of the lesions resulting in injury beyond the targeted perfusion bed.

CONCLUSIONS

Intracoronary ethanol ablation is a promising technique for the treatment of arrhythmias. Significant arrhythmias and a decrease in left ventricular ejection fraction are associated with this technique. Lesions are generally produced within the distribution of the targeted coronary bed, but are also frequently associated with reflux to a second vascular distribution.

Epicardial and subselective transcoronary chemical ablation of incessant ventricular tachycardia

Incessant ventricular tachycardia in patients with severely depressed ventricular function remains a major therapeutic challenge. Although alcohol ablation via the tachycardia related vessel has been shown to be an effective alternative, it might not be applicable in some cases due to anatomic limitations. In three patients with ischemic cardiomyopathy and incessant ventricular tachycardia no effective antiarrhythmic therapy could be found. Alcohol ablation was then attempted but the tachycardia related vessel could not be intubated. A subselective injection of alcohol into a more proximal segment of the coronary artery was then performed in two cases. In one patient as subselective injection was also not possible, the injection was performed epicardially after thoracotomy. Ablation was successful in all cases. In very selected cases of incessant ventricular tachycardia that have failed all other therapeutic interventions, alcohol ablation of the tachycardia can be performed using an epicardial or subselective transcoronary injection of alcohol.