Discussion

Coronary dissection is a very important diagnostic consideration for all peripartum acute coronary syndrome (ACS) presentations. The incidence of peripartum myocardial infarction is thought to be low, estimated at 6.2 per 100 000 pregnancies in one population-based study.1 In another series, coronary artery dissection was the cause of 43% of cases of peripartum myocardial infarction,2 highlighting this condition’s disproportionately higher incidence in patients who are currently or recently pregnant. The typical risk factor for this complication during iatrogenic cases—particularly pre-existing coronary disease—is not generally present in spontaneous peripartum cases.3 In the latter, variations in level of sex hormones are postulated to influence arterial structure4 while other groups have demonstrated a possible vasculitic component,5 perhaps due to changes in peripartum immune function. While the exact mechanism remains unclear, there appears to be a general consensus on an association of pregnancy-associated changes in the pathogenesis of dissection.

Regardless of the mechanism, when the index of suspicion is high that coronary dissection may occur or has already occurred, efforts must be made by the operator to limit the iatrogenic contribution to this problem. In general, iatrogenic causes of de novo dissection include catheter tip or guidewire trauma, vigorous contrast injection and angioplasty balloon overinflation.6–8 In the present case, the procedure was performed via radial access, which requires usually more complex catheter manipulation than the femoral route, potentially increasing the risk of inadvertent catheter trauma or deep vessel intubation. Similarly, force of contrast injection is an important procedural consideration, especially in pre-existing coronary dissection cases undergoing angiography. We use an automated contrast injection system, which could, in theory, help reduce risk of dissection or propagation by allowing the operator precise control over injection parameters (peak pressure, rate of pressure rise and volume). Current studies seem to suggest reduced contrast exposure and access site complications with the use of automatic contrast injectors,9 10 but further study and consensus guidelines would be helpful to determine what programmed settings of automatic injectors are most likely to reduce the risk of iatrogenic dissection and/or propagation.

Spontaneous coronary dissection remains an uncommon cause of myocardial infarction, and the optimal approach to management is a subject of ongoing study due to the low frequency of this condition and conflicting data. One of the larger retrospective studies of patients presenting with acute coronary syndrome due to spontaneous dissection found that the majority of patients could be safely managed conservatively in the absence of clinical instability or poor culprit vessel flow while percutaneous intervention (PCI) overall did not improve long-term vessel patency and was associated with a high complication rate and need for emergent bypass surgery.11 In another single-centre study, the authors also found poor procedural success rates with PCI and recurrent ischaemic events regardless of the treatment approach.12 Given the theoretical advantages of restoring normal vasomotion and endothelial function, a number of groups have reported successful use of bioresorbable vascular scaffolds (BVS) in patients presenting with spontaneous coronary dissection who were treated with PCI.13–15 While this seems a promising future strategy, the relatively bulky first-generation BVS systems preclude their use in tortuous or small vessel segments at present. The choice of medications used—dual antiplatelet therapy in the setting of infarction, beta blockers and ACE inhibitors—is based on their indications for atherosclerotic ACS and must take into account both current pregnancy and lactation status. The use of thrombolytics has also not been systematically studied, but is controversial due to the theoretical possibility for dissection/haematoma extension.12

In summary, utmost care must be taken by the operator to minimise the risk of propagation during angiography in the setting of ACS when the risk of spontaneous coronary dissection is high. The role of newer technologies such as automated contrast injection systems in reducing this risk remains to be determined. The choice of therapy must be individualised based on clinical stability to ensure best clinical outcome for both mother and child.