Complex ventricular arrhythmias are among the most difficult for electrophysiologists to manage.
Ventricular tachycardia is potentially lethal and can result in frequent shocks in patients with defibrillators. Antiarrhythmic drugs are frequently incompletely effective and have potentially serious adverse effects. Radiofrequency ablation (RFA) of ventricular arrhythmias is typically complex with suboptimal efficacy. Fortunately, new techniques have made RFA an increasingly attractive treatment option for patients with symptomatic or refractory ventricular arrhythmias.
One important difficulty is the development of unstable hypotension when ventricular tachycardia is induced for mapping purposes, limiting the ability to accurately pinpoint the arrhythmogenic zones of slow conduction.
Mayo Clinic is among the first institutions in the United States to use a microcirculatory axial blood flow pump in patients with hemodynamically unstable ventricular tachycardia. This pump is a miniaturized percutaneous cardiac assist device, providing circulatory support during sustained ventricular arrhythmias. This support permits prolonged mapping of the arrhythmia and increases the chances of a successful ablation.
The pump is placed via the femoral artery, across the aortic valve into the left ventricle with use of fluoroscopic and intracardiac ultrasound echocardiographic (ICE) guidance.
ICE is particularly helpful in monitoring function of the aortic valve and position of the pump within the left ventricle. Forward flow in the systemic circulation is approximately 2.5 L/min. Although this flow is markedly less than normal cardiac output and vasopressors have been administered for additional hemodynamic support, patients have shown no signs of organ hypoperfusion despite lengthy procedures.
Potential complications that may occur with use of this device include vascular damage, increased ectopy (including nonclinical ventricular arrhythmias), difficult catheter manipulation, aortic valve dysfunction, and thromboembolic events. This early experience has included younger patients without serious comorbid conditions such as renal dysfunction. Other factors may contribute to the success or failure of ablation attempts in these patients.
This early experience at Mayo Clinic is encouraging, although wider application and long-term follow-up will be required to determine appropriate indications for this approach.