Hardware for the Heart: The Increasing Impact of Pacemakers, ICDs, and LVADs

We recommend contacting and discussing the care of patients who present after ICD shocks with the treating electrophysiologist or cardiologist whether or not the shock is considered appropriate.

Patients who have an ongoing arrhythmia when evaluated emergently should be managed according to advanced cardiac life support (ACLS) guidelines, regardless of the presence of an ICD,¹ particularly in cases of cardiac arrest from a non-shockable rhythm.

Initially, the shocks should be presumed to be appropriate. Presence of VT/VF in setting of shock would be consistent with appropriate shock delivery. Next, the clinician needs to consider if shock delivery was effective and if it achieved termination of malignant ventricular arrhythmia. Patients with persistent VT/VF despite delivery of a shock may have ICDs with inadequate voltage in the batteries to terminate; external shocks and intravenous (IV) antiarrhythmic medications may be required and should be administered per ACLS guidelines.

When patients present with multiple shocks, the shocks are typically appropriate and often triggered by episodes of VT/VF. Treatment of the underlying causes is the priority; the patient may have sustained or recurrent VT/VF as a result of an acute event, such as cardiac ischemia, hypokalemia, or severe acute heart failure exacerbation. Aggressive reperfusion, management of potassium imbalance, and circulatory support are paramount.

Inappropriate shocks most commonly are delivered for supraventricular tachycardias such as atrial fibrillation that is incorrectly interpreted by the ICD as VT/VF. In these cases, the treatment is the same as for a patient without an ICD (eg, IV diltiazem to slow atrial fibrillation with rapid ventricular response).

In patients experiencing multiple inappropriate ICD shocks, the device can be immediately disarmed by placing a magnet over the ICD pocket until the electrophysiologist can reprogram it. This will not inhibit baseline/backup pacing. However, while a magnet is in place, neither supraventricular tachycardias nor VT/VF will be detected.¹ If appropriate shock delivery has been performed for ventricular dysrhythmia, these patients must remain on a cardiac monitor under close medical observation. It is good practice to assume device failure after application of a magnet, and appropriate management strategies include placing external defibrillators pads on the patient’s chest. Fortunately, most ICDs will resume normal function following magnet removal.

In the Canadian Journal of Cardiology (1996), Kowey defined electrical storm as a state of cardiac electrical instability characterized by multiple episodes of ventricular tachycardia (VT storm) or ventricular fibrillation (VF storm) within a relatively short period of time.^28,30,31,32
In the patient with an ICD, the generally accepted definition is occurrence of two or more appropriate therapies (antitachycardia pacing or shocks) in a 24-hour period. Triggers may include drug toxicity, electrolyte disturbances (hypokalemia and hypomagnesemia being the most common culprits), new or worsened heart failure, or myocardial ischemia, which account for more than a quarter of all episodes. Electrical storm usually heralds a life-threatening acute pathology placing these patients at immediate high risk of death.²⁸ Immediate communication and consultation with the electrophysiology team is recommended.

Left Ventricular Assist Devices: From Mystery to Mastery

Alicia S. Devine, JD, MD

Dr Devine  is an assistant professor, department of emergency medicine, Eastern Virginia Medical School, Norfolk.

Disclosure: The author reports no conflict of interest.

Approximately 5.7 million people in the United States have heart failure, and complications from heart failure represent 668,000 ED visits annually. Heart failure is the primary cause of death in 55,000 people each year. Half of patients die within 5 years of being diagnosed with heart failure.¹

Heart failure is initially managed medically; however, some patients become refractory to medical treatment and require heart transplant. Unfortunately, the demand for donor hearts far exceeds the supply, and patients can spend a long time waiting for a donor heart. In addition, not all patients are candidates for transplantation. Left ventricular assist devices are mechanical devices implanted in patients with advanced heart failure in order to provide circulatory support when medications alone are not efficacious. LVADs have been associated with improved survival for heart failure patients.

There are generally two indications for LVAD support: as a bridge to transplant for patients waiting for a donor heart, or as destination therapy for patients who are not candidates for heart transplant. Some patients have had improvement in their cardiac function after LVAD implantation and are able to have the LVAD explanted, leading to a third use for LVADs: bridge to recovery.

LVADs have been in use for over 30 years, and they have evolved during that time to become smaller in size with much fewer complications. Initial models operated with a pulsatile-flow pump that, while adequate in terms of blood flow, contained several parts susceptible to breaking down. Early models were large and cumbersome, especially for smaller patients. New-generation LVADs use a continuous-flow design with either a centrifugal or an axial flow pump with a single moving part, the impeller. The continuous-flow LVADs are quieter, smaller, and significantly more durable than the earlier, pulsatile-flow LVADs. These improvements have expanded the pool of eligible patients to include children and smaller adults.² Moreover, continuous-flow LVADs provide greater rates of survival and quality of life than the earlier pulsatile-flow models.³