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SPONTANEOUS CORONARY ARTERY DISSECTION
06 January 2014
BCS Editorial
By: Azeem S Sheikh
Co-Author:Rizwan Ahmed Background
Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome (ACS), mainly affecting fairly young otherwise healthy and predominantly but not exclusively female patients1,2. The underlying pathophysiology is unknown and although anecdotal associations have been reported, until recently there has been little systematic data on the presentation, management and outcomes of patients with this condition. A recent international collaboration between UK/EU researchers (http://scad.lcbru.le.ac.uk/) and US partners at the Mayo Clinic (http://www.mayoclinic.org/spontaneous-coronary-artery-dissection/) has been developed to study a sizeable cohort of patients with a view to a better understanding of all aspects of this condition. This research programme is actively seeking to recruit incident and prevalent cases of SCAD (via the web-portals above).
Pathogenesis
The pathogenesis of SCAD is unknown. The condition is characterised by the development of an intramural haematoma that usually runs in the outer media or between the media and adventitia of the coronary artery, resulting in haemodynamic compromise due to the resulting external compression on the lumen3.
Although coronary dissection can occur in patients with atherosclerotic coronary disease, there is a distinct population where dissection occurs in the absence of co-existent atherosclerosis and therefore is truly ‘spontaneous’4. A dissection flap is frequently not present even on intracoronary imaging suggesting in some cases at least, the pathological mechanism may be spontaneous intramural haematoma formation rather than true dissection. A number of potential risk factors have been anecdotally reported. In addition to female sex hormones, these include increased shear stress (such as after exercise), connective tissue disorders disorders (including Marfan and Ehlers-Danlos syndromes) and cocaine use5.
Epidemiology
SCAD is a rare condition reported in 0.2% - 1.1% of patients undergoing coronary angiography. However interpretation of these figures is complicated by the variable inclusion of atherosclerotic plaque associated dissection which is not ’true’ SCAD. The condition affects predominantly young adult patients with mean age of 30-45 years at presentation. At least 70% of SCAD cases are women and 26 - 38% of cases occur in late pregnancy, peripartum or postpartum. The reported incidence of involvement for the left anterior descending coronary artery (LAD) is 57-75%; the right coronary artery (RCA), 20-32%; the left circumflex (LCx) 4-21% and the left main (LM), <1-21%6, 7. Multi-vessel SCAD is rare but have been reported.
Clinical Presentation
The clinical presentation of SCAD depends on the site and extent of the coronary dissection and the degree of restriction of coronary blood flow. It is possible some dissections may be asymptomatic. Most clinically evident SCAD events present with acute chest pain syndromes ranging from unstable angina (7%), non ST-elevation myocardial infarction (NSTEMI – 44%) to ST-elevation myocardial infarction (49%)6. In some patients myocardial ischaemia leads to ventricular arrhythmias and sudden cardiac death. In autopsy series the prevalence of SCAD in deaths in pregnancy complicated with myocardial infarction has been reported as 27%8.
Diagnosis
Diagnosis is invariably made at coronary angiography. Although patients may present with clear angiographic evidence of a dissection flap and extending spiral false lumen, these features are frequently absent. Angiographic misdiagnosis may be common and a low index of suspicion is recommended, particularly in patients presenting acutely at low risk of atherosclerotic coronary disease. Diagnosis can frequently be confirmed by intracoronary imaging (e.g. with intravascular ultrasound or optical coherence tomography)9. CT coronary angiography has also been described in cases of SCAD.
Figure: Angiographic appearance of spontaneous coronary artery dissection of the left anterior descending coronary artery causing luminal restriction (arrows) (A). Optical Coherence Tomography (OCT- catheter C) of dissection with true lumen (TL) and false lumen (FL) (B and C). Management
There are currently no known specific treatments for SCAD either to address the acute event or for longer term prevention. Acute management is focused on the immediate restoration of coronary blood flow where this is restricted and on supportive care following myocardial infarction. Chronic therapies are directed at the prevention of adverse cardiac remodelling following myocardial infarction.
When there is no evidence of ongoing ischaemia or haemodynamic instability, SCAD can reportedly be managed conservatively with complete angiographic resolution. Where coronary flow is reduced, reperfusion strategies become necessary8. Thrombolysis for SCAD has been described but with reports of adverse outcomes in some cases9. Percutaneous intervention (PCI) with stenting is frequently used to re-establish coronary flow. However, there are some PCI challenges specific to SCAD and complications, particularly technical failure are reported to be high10. For example, there may be difficulty in manipulation of a coronary guidewire into the true lumen which may be aided by use of intracoronary imaging. There is also a risk of haematoma propagation during stenting for SCAD and long segments of stents may be required to provide sufficient luminal scaffolding in SCAD. For this reason drug eluting stents are usually used, although there is no specific data to support their use for this indication.
Coronary artery bypass grafting is usually reserved for multi-vessel
disease, left main involvement or cases where there are specific anatomical challenges to percutaneous approaches (for example where there is complete vessel occlusion or it has proven impossible to pass a coronary guidewire into the true lumen).
The optimal long term therapy after SCAD is unknown. No clinical trials have been reported to date. There is a good rationale for therapies used to limit adverse cardiac remodelling following acute myocardial infarction (angiotensin converting enzyme inhibitors or angiotensin receptor antagonists, beta-blockers, aldosterone receptor antagonists). Antiplatelet therapies are indicated where stents have been used but their role in patients without stenting is unknown. The role of statins following SCAD is unknown.
Prognosis
In-hospital mortality of SCAD is relatively low, with a mean rate of around 3% (0-4%)6. Patients who survive the acute phase were initially thought to have good long- term prognosis, with a very low recurrence rate of SCAD or acute coronary syndrome and a 95% 2 year survival rate. However a recent series has suggested the longer term outlook may not be benign with recurrent SCAD in 17% (median follow-up 47 months) and an estimated 10-year MACE of 47%6. It is currently unknown in SCAD patients are at risk of other non-coronary events although an increased prevalence of femoral fibromuscular dysplasia has been reported, suggesting the arteriopathy in SCAD may not be localised5,6.
Conclusions
Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndromes and as such, although many cases are described, there remains little reliable information on the epidemiology, optimal clinical and interventional management and outcomes of this condition. There has been little systematic research to date into SCAD, although a current international collaboration seeks to systematically address some of the key questions about this condition.
References
- Vanzetto G, Berger-Coz E, Barone-Rochette G, et al. Prevalence, therapeutic management and medium-term prognosis of spontaneous coronary artery dissection: results from a database of 11,605 patients. Eur J Cardiothorac Surg 2009;35:250-4.
- Mortensen KH, Thuesen L, Kristensen IB, et al. Spontaneous coronary artery dissection: a Western Denmark Heart Registry Study. Catheter Cardiovasc Interv 2009;74:710-7.
- De Maio SJ. Clinical course and long-term prognosis of spontaneous coronary artery dissection. Am J Cardiol 1989;64:471-4.
- Parry R, MacConnell T, Wilde P. Case report: spontaneous coronary artery dissection. Clin Radiol 1994;49:142–3.
- Saw J, Ricci D, Starovoytov A, Fox R, Buller CE. Spontaneous coronary artery dissection: prevalence of predisposing conditions including fibromusculardysplasia in a tertiary center cohort. JACC Cardiovasc Interv. 2013Jan;6(1):44-52.
- Tweet MS, Hayes SN, Pitta SR, Simari RD, Lerman A, Lennon RJ, Gersh BJ, Khambatta, S, Best PJ, Rihal CS, Gulati R. Clinical features, management, and prognosis of spontaneous coronary artery dissection. Circulation. 2012 Jul 31;126(5):579-88.
- Kamineni R, Sadhu A, Alpert JS. Spontaneous coronary artery dissection: report of two cases and a 50-year review of the literature. Cardiol Rev 2002;10:279-84.
- Roth A, Elkayam U. Acute myocardial infarction associated with pregnancy. J Am Coll Cardiol. 2008 Jul 15;52(3):171-80.
- Adlam D, Cuculi F, Lim C, Banning A. Management of spontaneous coronary artery dissection in the primary Percutaneous coronary intervention era. J Invasive Cardiol. 2010 Nov;22(11):549-53.
- Zupan I, Noc M, Trinkaus D, Popovic M. Double vessel extension of spontaneous left main coronary artery dissection in young women treated with thrombolytics. Catheter Cardiovasc Interv. 2001 Feb;52(2):226-30.
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