For patients with recurrent fainting, quality of life can take a hit. While around a third of the population will experience fainting (also called syncope) at least once in their lifetime, repeated episodes can prove hard to manage, and may point to an underlying problem
One 2006 study found that serious accidents (such as fractures and car crashes) have been reported in 6% of patients with syncope, while 12% have experienced soft tissue injury and 29% laceration and bruises. In patients with heart disease, fainting episodes can be a warning sign, pointing to an increased risk of sudden death. It’s critical, then, that patients receive a proper diagnosis and prevention techniques.
Luckily, the most common cause of recurrent fainting is also one of the most benign. Vasovagal syncope, also called reflex syncope, occurs when the blood vessels open wide (vasodilation) and blood pressure drops (hypotension) at the same time as the heart rate slows down (bradycardia). This can lead to a temporary loss of consciousness, with not enough blood reaching the brain.
Vasovagal syncope does not, in itself, signal a problem with the heart, and it can usually be managed with lifestyle changes. However, in extreme cases it can give rise to an asystolic pause (a long pause between heartbeats) – otherwise known as asystolic vasovagal syncope. In these cases, patients may require a pacemaker.
“Patients suffering from recurrent syncope often have to deal with stressful episodes that result from their condition,” says Professor Michele Brignole of the Istituto Auxologico Italiano, Ospedale San Luca. “Syncopal episodes often cause severe trauma and limit the daily activities.”
How closed loop stimulation works
In September, Berlin-based medical devices company Biotronik announced results from a major trial that could affect how these patients are treated. Patients with asystolic vasovagal syncope were given a dual-chamber pacemaker, incorporating Biotronik’s closed loop stimulation (CLS) algorithm.
Compared to a conventional pacemaker, a pacemaker fitted with CLS is better able to help the patient cope with physical and mental stress. It monitors the heart’s contractility (its mechanism for controlling stroke volume) with each beat, and adjusts to the patient’s needs automatically.
“In comparison to a pacemaker that only paces at a fixed lower rate when the patient’s heart rate is below this value, CLS paces the heart at different heart rates depending on the metabolic demand of the patient,” says Brignole, who led the BIOSync study. “These pacemakers are equipped with sensors that monitor the changes in the body’s physiologic conditions. The higher the metabolic demand – e.g. during exercise – the higher the pacing rate.”
Once the pacemaker is fitted, the CLS sensor sends tiny pulses of current to the right ventricle. It measures the impedance signal just after the heartbeat, to create a picture of what the heartbeat looks like at rest.
“The impedance curves obtained during exercise are compared to baseline impedance curves obtained while the patient is at rest. The time-integrated difference between the exercise and baseline impedance waveforms is converted to the pacing rate,” explains Brignole.
He adds that CLS provides instant and reliable heart rate adaptation, in response to both exercise and non-exercise metabolic demand. It also adapts automatically to patients’ changing needs – due to drug treatment, for example.
The study results
While Biotronik’s CLS sensor has been around for more than 20 years, this is the first time it has been tested extensively in patients with recurrent fainting.
Until now, the core patient group has been ‘chronotropic incompetent’ patients – i.e., patients whose heart rate does not increase sufficiently during exercise or other stresses, and need help stimulating the heart at higher rates. It is also effective in patients with sick sinus syndrome, who have problems with the body’s natural pacemaker, the sinus node.
Right from the outset, doctors wondered whether CLS might be useful in vasovagal syncope treatment, and small studies got underway. However, the latest study – called BIOSync – is the largest and best designed of the bunch. A double-blinded, randomised and placebo-controlled trial, the study enrolled 127 patients across 24 centres, with an average follow up of 11.2 months. It took place between 2015 and 2020.
The results were compelling. Compared to the placebo group, who received a conventional pacemaker, the CLS-paced patients saw clear improvements in their symptoms. After two years, syncope recurrence rate was reduced by 77%, and the combined rate of syncope and pre-syncope (the sensation that you’re going to faint) was reduced by 56%.
“Dual-chamber pacemaker therapy can compensate for the bradycardia and thus sometimes prevent loss of consciousness and related subsequent injury to the patient,” says Brignole. “Pacemakers with CLS may be particularly effective because they adapt the pacing rate to the contraction dynamics of the right ventricle and can therefore intervene directly and much quicker in the generation mechanism of the vasovagal syncope.”
Better diagnostics and treatment
The study also found that tilt-table testing – used to evaluate the cause of unexplained fainting – is a good way of determining which patients need a pacemaker. Up till now, the practice was controversial, with trials showing mixed results.
“The estimated benefit of dual-chamber pacing in cardio inhibitory tilt-positive patients is stated to be weak in the current ESC guidelines; divergence of opinion exists among experts,” says Brignole. “The BIOSync study has strengthened the body of evidence showing that tilt testing is a useful method to select pacemaker candidates. It provides valuable insights into how tilt-testing can be used as a reliable approach – adding more alternatives to physicians’ arsenal when tackling complex cases.”
As and when a patient does need a pacemaker, the BIOSync study suggests that closed loop stimulation has the edge over the alternatives.
“It will support the use of CLS in these patients over other dual-chamber pacing modalities for which no such beneficial data exist,” says Brignole. “Knowing that there is an effective and reliable treatment can bring much needed peace of mind.”