Heart of The Matter

Ask the DOC

Implantable cardiac devices such as pacemakers and defibrillators are very common these days, but these life-saving devices are very different as are the indications for their use. The heart has its own pacemaker, called the SA node, located in the upper chamber, or atrium. It generates an electrical impulse that causes the atrium, then the ventricle, or lower chamber, to contract, thereby generating a heartbeat. For reasons that are still not clear, the SA node may fail to generate an impulse, or that impulse may be blocked somewhere along the electrical pathway. This causes a slow heart rate, or bradyarrhythmia. The patient may feel very fatigued. Once the problem is diagnosed by an EKG, a pacemaker may be inserted to correct the heart rate. Usually inserted under the skin in the upper left chest, a wire called a lead is threaded through a main vein into the right ventricle, where it is anchored. Occasionally, wires must be threaded into both ventricles. This scenario uses a bivent(ricular) pacemaker.

Implantable cardiac defibrillators (ICDs) are used for shocking the heart in the same manner as defibrillator paddles that are used externally. If you watch medical shows, you’ve seen this simulated many times. Patients who have had heart attacks or who have other problems that cause the heart to enlarge and pump blood poorly have a condition called a cardiomyopathy. When the ejection fraction (EF), a measurement of the heart’s pumping efficiency, falls below 20 percent (normal EF is 60 to 65 percent), the risk of fatal arrhythmias like ventricular tachycardia and fibrillation rises dramatically. For this reason and others, an ICD may be implanted. The method of implantation is similar to a pacemaker, but an ICD has 2 leads, or wires. ICDs are implanted in the upper chest or left side. The electrical jolt from an ICD ranges from barely noticeable to a strong shock that may knock a person off their feet. A condition where an ICD is giving repeated shocks is called an ICD storm and immediate medical attention is a must.         

First described in 1968, a condition that causes pacemaker or ICD failure is called Twiddler’s, or Fiddler’s, syndrome. It is rare, seen in up to 7 percent of pacemaker and ICD failures, and usually within one year of implantation. It is most commonly seen in elderly ladies who have impaired cognition, or dementia. Older women tend to have looseness or laxity of the subcutaneous tissues like muscles. They may consciously or unconsciously fiddle with the device, often twirling it around under the skin. This causes the leads to be displaced and coil up. Depending on where the leads wind up, symptoms may vary. Symptoms may include dizziness, fatigue, syncope (loss of consciousness), slow heart rate, involuntary muscle twitching in the upper abdomen or left arm, hiccups, of involuntary respiratory spasms (due to stimulation of the diaphragm). Twiddler’s can be easily diagnosed by EKG and chest X Ray, which can show the coiled and displaced wires. The cure is either replacement of the device or re-anchoring of both the device and the leads.

Lastly, pacemakers and ICDs are programmed by using magnets. Therefore, any device that creates a magnetic field, for example a cellphone, should always be placed more than 6 inches from the implanted device. This includes metal detectors and metal-detecting wands. They can cause the device to malfunction. If you have one of these devices, ask for a manual pat-down instead.

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