A pacemaker could help prevent unpredictable fainting caused by missed heartbeats

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Fainting affects one in two people during their lifetime.

Those with recurrent episodes are often afraid to socialise or go to work.

Today researchers report the first effective therapy. The late breaking research is presented at ESC Congress 2020.

Fainting is caused by a fall in blood pressure and/or number of heart beats. In some patients, a trigger is identified — for example emotional stress, standing in a hot, crowded space or sitting up too quickly — and they have warning signs such as weakness, nausea, and dizziness.

But in many others, especially older adults, no trigger is found and there are no warning signs.

“This unpredictability raises the risk of falls and even serious trauma and people end up in the emergency room,” said principal investigator Professor Michele Brignole of the Faint and Fall Programme, Istituto Auxologico, Milan, Italy.

“If it happens repeatedly, it has a major impact on quality of life — at the same magnitude as a chronic disease.”

Currently there is no specific therapy and patients usually receive only generic advice on prevention, such as keeping hydrated, avoiding hot crowded environments, tensing the muscles, and lying down.

But prevention is particularly difficult if there are no warning signs.

The BIOSync CLS study examined whether a pacemaker could prevent unpredictable fainting caused by missed heart beats.

Patients with this particular cause of fainting were identified using tilt testing. This involves lying on a table that is slowly tilted upward to simulate standing up. Blood pressure and heart rate are monitored during the examination.

The study included 128 patients aged 40 and above who had fainted at least twice in the previous year with no warning signs. A tilt test showed that fainting was caused by missed heart beats.

All study participants received a pacemaker — but they were randomly allocated to having the pacemaker switched on (pacing group) or switched off (control group). They were then followed-up for fainting episodes.

During a median follow-up of 11.2 months, more than half of patients (53%) in the control group fainted compared to just 16% in the pacing group.

This translated into a 77% lower risk of fainting in the pacing group.

The researchers estimated that at two years, two-thirds (68%) of the control group would have a fainting episode compared to one-fifth (22%) of the pacing group.

A pacemaker would provide a 77% relative risk reduction of fainting over two years and a 46% absolute risk reduction.

Just over two patients (2.2) would need to receive a pacemaker to prevent fainting. Put another way, if 11 patients received a pacemaker, fainting could be avoided in five patients.

Implanting the pacemaker caused minor adverse events in five patients (4%) such as lead-related complications.

Professor Brignole said: “Our study shows that pacing can be an effective treatment for selected people with unpredictable fainting episodes. Tilt testing is a simple and non-invasive way to identify people who could benefit. We hope this new treatment option will enable these patients to resume a normal life without fear of blackouts.”

Funding: The study was funded by Biotronik SE & Co. KG, Berlin, Germany.


There are many conditions that can cause fainting, but a nervous system reflex is often responsible. Certain triggers—for example, standing in a hot, crowded area—can cause blood pressure to fall, and with it, blood flow to the brain. The person may or may not feel faint or nauseated before blacking out.

Three forms of syncope

There are three forms of this condition, called “vasovagal syncope.” (Syncope is the medical term for loss of consciousness.) In people with vasodepressor syncope, blood pools in their legs, blood pressure falls, and the person passes out. If it happens often, medications and salt can be used to keep blood pressure up.

Some people, however, lose consciousness because their heart rate suddenly slows to fewer than 40 beats per minute (BPM). It may even stop for several seconds—a situation called asystole (pronounced like “ay-sis-toe-lee”).

This causes their blood pressure to drop, and the person to pass out, usually without warning. This form is called cardioinhibitory syncope.

Some people have a combination of both types, called mixed syncope.

A new solution

With no medications to prevent the heart rate from suddenly dropping, cardioinhibitor syncope has not been easily treatable, and fainting eipsodes have not been preventable. But now there is hope for some individuals.

A study reported in the May 29, 2012 issue of Circulation found that a dual-chamber pacemaker—so named because it paces the right atrium and right ventricle—reduced fainting episodes by 57% in people with asystole lasting six seconds or more.

These special pacemakers can detect an abrupt drop in heart rate of 20 BPM, or a rate that falls below 40 BPM, and compensate by pacing the heart at a faster rate for a fixed amount of time. This helps maintain blood pressure and prevents fainting.

Unfortunately, dual-chamber pacemakers are not effective for vasodepressor or mixed syncope. But for people with cardioinhibitor syncope, they bring hope for avoiding sudden, potentially dangerous, fainting episodes.

“It does not cure the problem, but the overall picture is better than it was before,” says Dr. Peter Zimetbaum, director of clinical cardiology at Beth Israel Deaconess Medical Center and an associate professor of medicine at Harvard Medical School.


Source: European Society of Cardiology

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