Discussion

SCAD is a rare aetiology of acute coronary syndrome (ACS) seen in women. Early retrospective studies suggested approximately 30% of SCAD cases; however, more recent reviews suggest that pregnancy-related SCAD accounts for less than 5% of SCAD cases.3 SCAD is defined as a non-traumatic and non-iatrogenic formation of a false lumen due to the separation of the coronary arterial walls resulting in an intramural haematoma (IMH).4 There are two commonly accepted theories regarding the formation of the IMH. One theory is a tear in the intima resulting in blood entering from the endoluminal space to the intimal space, creating a false lumen.4 The second proposed mechanism of IMH formation is due to rupture of the vasa vasorum, which are the small arterioles within the walls of arteries supplying blood to the wall resulting in blood pooling within the intramural space creating a haematoma.4 The pathophysiology remains largely unknown but is likely a combination of predisposing factors that precipitate SCAD.5

This case of SCAD presented in a young healthy woman with no significant medical history except for the use of daily e-cigarettes for several years. The peripartum and postpartum state is associated with hormonal changes, which increase the risk of weakening the arterial walls of the heart increasing the risk for SCAD.1 4 The postpartum state is associated with an elevation of progesterone leading to weakening of the tunica media, increasing the risk of dissection.4 Oestrogen, which has a protective effect against atherosclerosis and ischaemic injury of the myocardium, falls after parturition.1 4 Thus, it can be hypothesised that as progesterone levels rise and oestrogen levels, fall there is an increased risk of SCAD.

The patient’s history of daily e-cigarette smoking during her partum and postpartum period also potentially increased her risk for SCAD. E-cigarettes are aerosolised mixtures of glycerin, propylene glycol, nicotine and flavouring additives, thus delivering nicotine by inhalation in the absence of combustion.2 The long-term effects of e-cigarette are currently not well known; however, a recent review article has found that some e-cigarette emit chemical levels similar to traditional tobacco cigarettes and thus may not be as safe as reported.3 Further research on the cardiovascular safety of e-cigarettes is warranted. However, habitual e-cigarette smoking has been linked with an increase in cardiac sympathetic activity and oxidative stress, which can predispose patients to cardiac events.2

SCAD has been associated with precipitating stressors that raise catecholamines, which can increase cardiocirculatory shear stress that can predispose to SCAD.3 Emotional and mechanical stressors have also been linked to higher-than-expected proportion of cases of SCAD.4 5 Tobacco cigarette use is associated with increased sympathetic stimulation resulting in increased heart rate and increased blood pressure.6 In addition, smoking results in increased carboxyhaemoglobin leading to decreased oxygen-carrying capacity.6 In turn, this can lead for the need for increased oxygen demand for the heart resulting in increased risk for myocardial ischaemia. Previous case reports have associated SCAD in patients who were daily tobacco and cannabis smokers, and it is plausible that e-cigarette smoking can also increase the risk for SCAD based on similar mechanisms.5–9 In this patient, the postpartum state in combination with e-cigarette usage may have increased her risk for developing SCAD due to increased catecholamine release. Nicotine has been shown to promote atherosclerosis in vitro, as well as an increase in diastolic pressure,10 which may further weaken coronary artery endothelium.10 11Less than 4% of cases of SCAD present with focal atherosclerotic stenosis such as this patient and are classified as type 3 lesions.5 Physicians should strongly discourage e-cigarette smoking in pregnant women as its long-term effects are currently unknown but may increase the risk for cardiovascular events. Buccal and transdermal nicotine should be offered as alternatives as there is slower absorption and increased first-pass metabolism resulting in less abuse potential.

SCAD should be considered as an aetiology of ACS in young women who present with chest pain. This case illustrates a young woman with an e-cigarette smoking history who presented after an uncomplicated pregnancy. The hormonal changes during the postpartum period in addition to the effects of e-cigarette smoking may have led to weakening of the patient’s arterial walls predisposing the patient to an increased risk for dissection of her LAD in addition to premature atherosclerosis from increased nicotine exposure.