Driving and exercise in patients with ICDs

November 12, 2003

Orlando, FL - US doctors have found that driving is rarely associated with triggering the discharge of implantable cardioverter defibrillators (ICDs). And when this did occur, it was most likely to happen within 30 minutes after driving rather than while driving.

The same researchers also report that moderate exertion increases the risk of triggering an ICD shock, particularly in those who are usually sedentary.

Dr Christine M Albert (Massachusetts General Hospital, Boston) reported the findings on driving from the Triggers of Ventricular Arrhythmias (TOVA) study, a multicenter study of triggers of ventricular arrhythmias among patients with ICDs, here at the American Heart Association Scientific Sessions.

Only 38 of the 1188 patients included in the study reported driving a car within the hour before ICD discharge. These people were more likely to have been driving for longer periods each week than those who did not get shocked, Albert noted. And because shocks were more likely immediately after driving, she told heartwire , it may be prudent for patients with ICDs to rest for a while after driving, particularly if they are going on to do some other strenuous or stressful activity.

A previous study published in the New England Journal of Medicine in 2001 found that 8% of 295 patients with ICDs received a shock while driving[1].

Albert said there are no nationwide recommendations on whether patients should drive following ICD implantation and that advice "varies from state to state." For example, in Massachusetts, those who have had syncope are not supposed to drive for six months, but there are no other restrictions, she noted.

 
Do people get into accidents if they have a shock while driving? We don't know this yet.
 

"We cannot make any recommendations on the basis of these data, however," she commented, "We need more information. For example, do people get into accidents if they have a shock while driving? We don't know this yet."

Is moderate exertion a trigger for ICD discharge?

The TOVA investigators also reported findings on moderate exertion in patients with ICDs. Dr Murray A Mittleman (Beth Israel Deaconess Medical Center, Boston) said it is known that vigorous physical exertion can trigger sudden cardiac death, presumably by precipitating life-threatening arrhythmias. But whether lower levels of exertion can cause such ventricular arrhythmias remains unknown, he said.

The 1188 patients in TOVA reported their habitual exertion patterns at entry and after six and 12 months of follow-up. Moderate exertion included activities such as brisk walking or stair climbing. Of the patients, 43% reported habitual moderate exertion at least three times a week. But a third of patients were "essentially sedentary," Mittleman said.

There were 153 discharges of ICDs in 95 patients, 21 (14%) of whom reported that their ICD had discharged during or within one hour of moderate exertion. Moderate exertion increased the risk of ICD discharge threefold, and the risk "seems to continue or may even be higher immediately after exertion," Mittleman noted.

Not surprisingly, the habitually sedentary were more at risk of receiving a shock when they undertook moderate exertion than those who were active on a regular basis. "It seems that habitual activity is going to be protective," Mittleman commented.

Even vigorous exercise may be safe in selected patients

Meanwhile, researchers from Yale reported a study on vigorous exercise in patients with ICDs. Dr Jennifer S Davids (Yale University School of Medicine, New Haven, CT) said current guidelines recommend restriction of exercise in patients with ICDs to low-intensity activities such as golf or bowling. But while the risks of vigorous sports have been postulated, the actual risk has not been evaluated, nor has the extent to which patients adhere to guidelines, she said.

Davids and colleagues conducted at telephone survey of all Yale ICD clinic patients under 71 without orthopedic or medical limitation to exercise. Of the 164 patients contacted, 10% reported engaging in vigorous activity such as tennis and basketball. Also, 17% said they regularly engaged in potentially dangerous activities such as biking, water sports, or skiing. Of the patients, 23 (14%) experienced a total of 36 shocks during vigorous physical activity. The only shock-related injuries were 2 skin breaks due to falling.

Davids concluded that sports involving vigorous physical exercise "may be safe in selected ICD patients."

Optimal follow-up schedule for ICD patients

German researchers at the AHA meeting reported that routine follow-up intervals of six months appear to be safe for patients with ICDs. Dr Julia C Senges-Becker (University of Heidelberg, Germany) and colleagues performed a comparative analysis on the detection of adverse events in 618 patients with ICDs, relying on information from every three-month visit or every other visit (six-month interval).

During follow-up of around three years, 137 adverse events occurred in 110 patients (17%). The mode of detection included ICD interrogation in 38, history/physical exam in nine, unplanned visits (patient initiated or due to manufacturer recall) in 47, and routine x-ray in 34 patients.

Regarding six-month rather than three-month follow-up intervals, a theoretical maximum delay of three months in the detection of potentially life-threatening adverse events would have occurred in 1.7% of all patients, Senges-Becker said. And for newer ICDs implanted after 1999, this figure would have been only 0.9%, she added.

She said that ICD-related adverse events detected during routine follow-up visits are relatively rare, particularly with the newer devices. Only nine of 618 patients owed the detection of their ICD-related adverse event to the physical follow-up visit, Senges-Becker said. Therefore, follow-up visits of six months appear to be safe, and there is potential to expand this out further by the use of telemetric ICD interrogation and electronic X-ray scan transmission, she concluded.

-LN

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