High spinal cord injury precipitating syncope: a rare indication for pacemaker insertion

Abstract

The current evidence for vasovagal syncope management is that cardiac pacing is only indicated in a highly select group of patients where symptoms can be linked to bradycardic episodes. High spinal cord injury can lead to autonomic dysfunction and sympathetic nervous system hypoactivity. A high spinal cord injury can theoretically precipitate profound bradycardia leading to haemodynamic instability and syncope. A patient in his 50s with a history of C2 spinal injury was admitted to our tertiary centre for management of what was initially thought to be septic shock causing hypotension and syncope. With evidence to suggest this patient’s presentation may be profound reflex syncope in the context of unopposed parasympathetic signalling, consensus was reached to implant a permanent pacemaker. Remarkably, the patient’s haemodynamics stabilised and there were no further episodes of syncope.

Background

The autonomic nervous system regulates cardiac output and vascular tone to maintain adequate perfusion to the body. A spinal cord injury can lead to aberration of the autonomic regulation of the cardiovascular system. Further, as a consequence of anatomy, a high spinal cord injury (above T6) can acutely lead to sympathetic hypoactivity and unopposed parasympathetic signalling. Sympathetic fibres higher than this level run in the spinal cord while parasympathetic fibres run in the vagus nerve. Therefore, high spinal cord injury acutely will cause neurogenic shock, seen clinically as hypotension with bradycardia.¹ In chronic spinal cord injury patients, there is autonomic dysreflexia, characterised by hypertension with bradycardia.¹

Sick sinus syndrome describes a group of diseases characterised by dysfunction of the sinoatrial node, resulting in bradycardia. Sinoatrial node dysfunction may be caused by reduced intrinsic automaticity, sinus arrest or a form of sinoatrial node block.² The consequence of sinoatrial node dysfunction can range from asymptomatic bradycardia to death. Based on current 2021 guidelines, the management options available to patients with bradycardia that causes symptoms are pharmacological agents or the insertion of a permanent pacemaker.³

In a patient with comorbid high-level spinal cord injury, the effect of unopposed parasympathetic signalling on the sinoatrial node may lead to profound bradycardia and syncope. We present the case of a patient admitted for management of symptomatic bradycardia precipitated by a chronic high spinal cord injury.

Case presentation

We present the case of a man in his 50s who was diagnosed 30 years ago with a traumatic C2 level spinal cord injury resulting in quadriplegia and ventilator-dependence. Our patient lives in a small rural town and is well known to their health services given his medical history of epilepsy and chronic infections, which included tracheostomy-related pneumonia and urosepsis. Three times in the past 4 years, this patient has been transferred to our tertiary centre for the management of sepsis. At the start of this year, this patient developed what was suspected to be septic shock requiring intensive care, and was, therefore, transferred to our tertiary centre. Despite his presentation of fevers and hypotension supporting a diagnosis of septic shock, he was incongruently found to be bradycardic, which was different to his previous presentations.

Initial investigation consisted of a panel of CT scan and a broad septic screen that revealed multiple sources of infection possibly explaining his shocked state. This included positive blood cultures with multiple coagulase negative Staphylococcus species, positive urine culture with extended spectrum beta lactamase-producing bacteria, near-complete consolidation of the right lung, a subphrenic collection, mastoiditis and a sacral pressure injury with superimposed infection. The patient was admitted to the intensive care unit (ICU) and commenced on meropenem therapy and underwent drainage of the abdominal collection. After 7 days of antibiotic treatment, there was significant improvement in his infective parameters, however, the patient continued to have episodes of symptomatic bradycardia with syncope, as can be seen in figure 1.

Figure 1.

Evidence of increased vagal activity. (A) ECG demonstrating sinus bradycardia with first degree heart block. (B) Episode of sinoatrial pause captured on telemetry. (C) Haemodynamic monitoring demonstrating transient drop in both heart rate and blood pressure concurrently. These three findings are highly suggestive of these episodes of bradycardia being vagally mediated. aVL, augmented vector left. aVF, augmented vector foot, aVR, augmented vector right. BP, blood pressure. HR, heart rate.

Treatment

On admission to the ICU, this patient was commenced on epinephrine infusion for suspected septic shock resulting in syncope; however, it became apparent that sepsis did not explain the patient’s presentation. Epinephrine, through its alpha-adrenergic and beta-adrenergic agonist effects, increases cardiac output and induces vasoconstriction, thus increasing blood pressure and mean arterial pressure, maintaining perfusion to the body. This patient responded well to epinephrine, however,when it was weaned, the patient became intermittently bradycardic and hypotensive. On day 3, fludrocortisone was added, which through its mineralocorticoid effect, increases sodium and water reabsorption to increase blood volume. Despite fludrocortisone, the patient continued to experience hypotension. On day 5, theophylline was added, a drug with a mechanism of action including phosphodiesterase inhibition and therefore positive inotropic effect, however, symptoms persisted. On day 7, midodrine was trialled, an alpha-adrenergic agonist, to determine if the underlying pathology was more likely to reflect orthostatic hypotension, however, the patient continued to experience syncope. After 14 days of not being able to wean epinephrine due to ongoing symptoms of bradycardia, hypotension, and syncope, atropine and glycopyrrolate were trialled, antimuscarinic agents that blocks the effect of parasympathetic signalling. These medications were seen to prevent bradycardia and the patient no longer experienced syncope. For the next day 10 days, when the patient became bradycardic, atropine and glycopyrrolate were given, and were seen to prevent syncope.

Given that sepsis was not driving the patient’s hypotension and he responded well to antimuscarinic agents, it was postulated that this might be a new diagnosis of his chronic high spinal cord injury driving profound bradycardia and syncope due to unopposed parasympathetic signalling. On vagal manoeuvers, the patient’s heart rate would fall into the 20s and he would experience syncope. Although there was evidence that his syncope was related to bradycardia and hypotension, vasodepressor driven pathology needed to be excluded in accordance with guidelines, as patients affected by peripheral vascular issues are unlikely to benefit from permanent pacing.³ Testing for a vasodepressor component of syncope is normally attained via tilt testing. Despite tilt testing not being appropriate for a patient in intensive care, evidence against vasodepressor driven syncope was already established, as the patient did not respond to midodrine. Therefore, the only option remaining was insertion of a permanent pacemaker.

The first multidisciplinary meeting was held on day 24 of his intensive care admission. The main concern regarding insertion of a permanent pacemaker was infection of the device. It was decided to wait until biochemical markers of infection normalised and infective endocarditis was ruled out before pacing would be considered. Echocardiography was performed and no vegetations were found. On day 29, with improving biochemical markers, temporary pacing wires were inserted to determine if pacing would provide a long-term solution. With an atrial paced rate of 70 beats per minute, the patient’s haemodynamics stabilised (figure 2). He was weaned off all blood pressure supports, and there were no further episodes of syncope. On day 31, a permanent pacemaker was inserted. No longer requiring ICU support, the patient was transferred to the ward. After 2 days of monitoring on the ward, the patient was discharged home with his carers.

Figure 2.

ECG demonstrating dual chamber pacing with resolution of bradycardia. aVL, augmented vector left. aVF, augmented vector foot, aVR, augmented vector right.

Outcome and follow-up

This patient received routine postpacemaker insertion follow-up, which showed that the pacemaker was working appropriately and the wound was healing well without evidence of infection. He had outpatient follow-up with cardiology 2 months postdischarge, and was found to be free from syncope without any device-related complications. Furthermore, on review by his neurologist, it was noted that the patient’s episodic confusion, which was labelled as epilepsy, also ceased following the insertion of the pacemaker. In retrospect, it was deemed that his symptoms and ‘postictal’ character were in fact likely caused by episodes of symptomatic sinus bradycardia. His antiepileptic medications were cautiously down titrated and no further episodes of ‘seizures’ occurred in the past 12 months. Unfortunately, this patient died 18 months postpacemaker insertion due to ventilator associated pneumonia, however, until this time, remained syncope free.

Discussion

Patients with a high spinal cord injury represent a particularly challenging group of patients with regard to refractory to vasovagal syncope. Due to the location of the injury in the spinal cord, the sympathetic fibres are damaged while the parasympathetic fibres (traversing through the vagal nerve) are left relatively unharmed. It has been shown that one in three patients with a high spinal cord injury will have sustained bradycardia due to unopposed vagal tone. Additionally, patients with high spinal cord injuries are at high risk of asystole during events that increase vagal tone, including suctioning or feeding.⁴ Additionally, our patient had recurrent sepsis, a condition known to drive venodilation and trigger a vasodepressor state. In patients such as ours, a single pharmacological agent or a pacemaker alone is unlikely to offset episodes of recurrent syncope. This highlights the importance of using both pharmacotherapies including vasoactive medications (midodrine, fludrocortisone), vagolytic medications (atropine and glycopyrrolate) in addition to consideration of a pacemaker with patients with refractory vasovagal syncope.⁵

A key consideration of whether pacemaker insertion is warranted in patients with refractory vasovagal syncope is what is the predominant mechanism causing a loss of consciousness. Vasovagal syncope can be classified as either predominantly cardioinhibitory or vasodepressor. Cardioinhibitory vasovagal syncope involves the patient having vagal episodes triggered by profound bradycardia and aystolic periods followed by a drop in blood pressure. Alternatively, vasodepressor syncope involves severe drops in blood pressure without a significant change in heart rate.⁵ It stands to reason that pacemakers would only be helpful in the patients with predominantly cardioinhibitory vasovagal syncope. The current guidelines support this, with the 2021 European Society of Cardiology Guidelines on cardiac pacing and cardiac resynchronisation therapy stating that there is class I evidence for pacing in patients above the age of 40 with severe unpredictable vasovagal syncope if they have documented symptomatic asystolic pauses lasting longer than three seconds, asymptomatic asystolic pauses lasting longer than 6 s, or asystolic pauses lasting longer than 3 s on tilt testing.

Therefore, cardiac pacing is only recommended in a small proportion of patients.³ After a multidisciplinary meeting and careful deliberation of the benefits and potential risks of pacemaker implantation in a patient with recurrent sepsis and syncope, the decision was made that our patient was a part of this small proportion that may benefit from permanent pacemaker insertion.

We present this case as an example of a situation in which pacing provided quality of life benefit to a patient with vagal driven syncope.

Learning points.

• Hypotension and syncope in patients with high-grade spinal injury can be due to the underlying pathophysiology of the spinal cord injury and exacerbated by vagal stimuli.

• Treatment of high vagal tone in spinal patients can include pharmacological agents that act as vagolytics (ie, atropine) and vasopressors (ie, midodrine).

• In refractory cases, pacemaker therapy may be indicated but requires a multidisciplinary approach including both cardiology and spinal medicine.

Ethics statements

Patient consent for publication

Consent obtained from parent(s)/guardian(s).