A shock from a heart device that saves people from sudden cardiac death may result in more health care, regardless of whether the shock was necessary, according to a new study.

An implantable cardioverter defibrillator, or ICD, delivers a shock to restore a normal rhythm when the lower chambers of the heart, or ventricles, beat erratically. Inappropriate shocks occur most often when the device mistakes a different heart rhythm problem for ventricular arrhythmia.

“ICDs cannot assess patients the way a doctor can,” said cardiac electrophysiologist Mintu Turakhia, M.D., senior director of research and innovation at the Center for Digital Health at Stanford University in California. “The device doesn’t know, for instance, if the patient is unconscious or has a pulse.”

For the study, researchers linked data transmitted to an ICD manufacturer with 10,266 patients’ healthcare records in 2008-2010. Of the 1,885 ICD shocks experienced by 963 people, 38 percent were inappropriate.

Researchers also found:

  • Nearly half of patients — 46 percent — who experienced a shock received health care related to the shock.
  • One in three patients received emergency room or outpatient care only.
  • One in seven patients was admitted to the hospital.
  • Invasive cardiovascular procedures, including electrophysiology studies, cardiac catheterization and cardiac ablation, were commonly performed after appropriate and inappropriate shocks.
  • The average cost of health care was $5,592 after an appropriate shock and $4,470 for an inappropriate shock.

“Obviously, shocks that save people’s lives are a good thing, but they are also very painful, can be traumatic and often lead to more healthcare procedures and expenses,” Turakhia said. “Fortunately, the industry has made many advancements in this area.”

Newer programming strategies reduce the number of inappropriate shocks, even among older-generation ICDs. The devices can be programmed by doctors to deliver fewer inappropriate shocks by waiting briefly to see if the dangerous heart rhythm resolves itself and by cautiously avoiding triggering shocks for heart rhythms with moderately fast rates.

“The quality of care is no longer just an issue of whether an ICD was implanted in appropriate patients, but also whether it was programmed in the best way possible,” Turakhia said. “We have the technology to do that today.”

The study is published in the American Heart Association journal Circulation: Cardiovascular Quality and Outcomes.