Syncope: red flags, loops and work-ups

PATIENTS with syncope can present a diagnostic challenge, but new technology is smoothing the way. InSight+ found out what’s changed and what’s stayed the same in the diagnostic work-up of patients with syncope.

What is syncope?

Syncope is defined as a temporary loss of consciousness usually related to insufficient blood flow to the brain.

The most common type of syncope is vasovagal syncope – the classic faint triggered by a phobia of needles or standing at assembly in the heat. It occurs in response to pain, stress or emotion and is largely benign.

Dr John Meulet, an electrophysiologist at John Flynn Private Hospital on the Gold Coast, where he chairs the medical advisory board, said the majority of the diagnostic work-up for vasovagal syncope involved taking a detailed history.

“There is often an event that triggers it, and there is a strong prodrome such as feeling warm or lightheaded,” he said.

Another relatively common cause of syncope is orthostatic hypotension – an abnormal blood pressure response to changing position, such as from lying down to standing. This can have neurogenic causes or be related to medications, especially some cardiovascular medications, antidepressants and antipsychotics.

However, the most serious causes of syncope are cardiovascular and neurological.

“These are the type a GP doesn’t want to miss,” Dr Meulet said. “Cardiac arrhythmias and structural heart diseases can usually be treated with a curative outcome, but that all depends on efficient diagnosis.

“Valvular heart disease as a cause of syncope, if not treated, has more than 30% mortality within 12 months,” he added.

What are the red flags?

The first red flag is the absence of a prodrome, Dr Meulet said.

“The most serious episodes of syncope are those which are unheralded and non-situational,” he said.

“Where there is no forewarning or prodrome, the patient needs to be referred to a cardiologist for further investigation as these are the type that are more likely to have cardiovascular or neurological causes.”

The other red flag for syncope that is “almost always sinister”, is when episodes occur mid-exercise, Dr Meulet said.

Other red flags are episodes of syncope associated with palpitations or irregularities of the heart, and those associated with family history of recurrent syncope or sudden death, according to the American Heart Association.

Determining the urgency

Dr Meulet said there were times when a patient with syncope should go straight to the emergency department (ED). For instance, if the patient had unheralded syncope at rest, looked unwell after the episode and had either tachycardia or bradycardia.

“They might be in a degree of heart block,” he said.

However, if there was no residual abnormality and the patient was completely conscious, pain free, and the electrocardiogram (ECG) was normal, Dr Meulet said the GP could afford to send the patient to the cardiologist for a Holter monitor, echocardiogram and review.

GPs could order the Holter and echocardiogram to streamline the cardiologist’s approach to the patient, Dr Meulet said.

“If a GP is worried, they can also organise a telehealth appointment with the cardiologist,” he added.

The diagnostic work-up

Dr Meulet said the most common diagnostic work-up was typically patient history and assessment, followed by ECG, echocardiogram and Holter, followed by a loop recorder, and, if there was still nothing apparent, referral to a neurologist for electroencephalogram (EEG) and magnetic resonance imaging (MRI).

Dr Meulet described how implantable loop recorders (ILRs) have significantly improved efficiency and diagnostic yield when it comes to managing patients with syncope in the past decade.

“Traditionally, what used to happen in the work-up of syncope is you’d have your ECG, [echocardiogram] and then Holter, and if the doctor wasn’t sure where to go from there they’d refer you to a neurologist,” he said. “You’d then have EEG, an MRI or [computed tomography] of your brain and then you’d be referred for a tilt test.

“The advent of [ILRs] closes the loop between when the patient has an event and what their heart rate and rhythm is doing,” he said.

Implanted just over the sternum and reading the ECG 24 hours a day, 7 days a week for 3 years, ILRs could enable the efficient diagnosis of tachycardia or intermittent heart block, Dr Meulet said.

Conversely, if the patient’s heart rhythm was completely normal during the episode of loss of consciousness, it could mean conditions such as blood pressure or epilepsy were the cause, he said.

“I’ve diagnosed three epileptics with the aid of ILRs because they were having a seizure that wasn’t affecting the heart rhythm,” Dr Meulet said.

Dr Meulet said the new technology had reduced ED readmission rates for patients with infrequent intermittent syncope.

“Typically, these patients would go to emergency again and again, getting the same ten tests each time,” he said. “Now if we put the [ILR] in after their first episode, when they come in after a second episode and you interrogate the device and download the information, you’ve got the diagnosis – you’ve broken that endless loop of going back to ED and staying for 48 hours on the monitor.”

Access issues

Professor Jonathan Kalman, head of the Royal Melbourne Heart Rhythm department agreed that ILRs could get patients “off the merry-go-round of recurrent ED presentations”.

However, he said, accessing the devices could be a problem, noting they could cost $3000 or more.

“There is very limited availability in the public hospital system,” he said. “In Victoria, the wait in some hospitals for an implant is many months.”

Dr Meulet said in his experience, the wait for an ILR in the public system could be “variable”, but insured patients could often access an ILR without a gap fee.

“Loop recorder implant is a day procedure fully reimbursed for the above indication with no out-of-pocket for my insured patients,” he said.

Dr Meulet added that Holter monitors typically involved only a small out-of-pocket expense, if any.

Other tests

Professor Kalman said an exercise test could be useful for patients with exercise-induced syncope or when a possible genetically determined arrhythmia syndrome was being considered.

Exercise tests should be performed at a centre with expertise to interpret and deal with the arrhythmia, Professor Kalman said.

“It is not the first line of tests a GP would perform,” he added.

Dr Meulet said tilt tests, which test the patient’s heart rate at different postures, were now “essentially obsolete” in the era of ILRs.

Professor Kalman agreed that tilt tests played only a minor role in today’s diagnostic process, but added that they could still be useful for patients with possible vasovagal syncope where you are looking to confirm the diagnosis.

“It may also help the patient to recognise transient prodromal symptoms that they had not yet appreciated,” he said.

Dr Meulet said a Holter monitor could be a useful screening tool in patients experiencing presyncope – the prodrome features of syncope but without fainting.

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