Canadian SCAD Study

Background:

Spontaneous coronary artery dissection (SCAD) is an under-diagnosed and poorly understood condition that frequently affects young women without conventional cardiovascular (CV) risk factors, and can result in myocardial infarction (MI), cardiac arrest, and death. This condition has been inadequately researched, with no prospective studies evaluating management strategies, assessing the presence and impact of predisposing and precipitating causes, or assessing its effects on short- and long-term CV prognosis. Furthermore, many people presenting with MI due to SCAD have been mis-diagnosed due to the limitations of the current "gold-standard" diagnostic test (coronary angiography) for this condition, resulting in erroneous diagnoses such as atherosclerosis, microvascular dysfunction, Takotsubo cardiomyopathy, coronary artery spasm, or "normal" coronary arteries. As such, clinicians are uncertain about how to diagnose, investigate and manage patients with SCAD, and similarly, patients are uncertain about how this condition will affect their subsequent lifestyle and long-term cardiac prognosis. Therefore, we propose a large prospective multicenter Canadian SCAD cohort study to ascertain the natural history according to predisposing arteriopathies and treatment strategy on long-term CV outcomes. The design of this study will secondarily improve the diagnosis of SCAD on coronary angiography by participating clinicians, and provide guidance on investigating predisposing conditions.

Preliminary Data:

We have enrolled 170 NA-SCAD patients in our registry at Vancouver General Hospital. We discovered a very strong association between NA-SCAD and fibromuscular dysplasia (FMD), with ~80% of these NA-SCAD patients diagnosed with concomitant FMD. Of patients who underwent coronary angioplasty/stenting, successful and durable results occurred in only 33%. Of patients treated medically, those who had repeat coronary angiograms all showed angiographic healing.

Primary Objective:

1. To evaluate the overall natural history of NA-SCAD: (a) the overall in-hospital and long-term CV outcomes with NA-SCAD, (b) the prevalence and effects of predisposing arteriopathies on in-hospital and long-term CV outcomes, (c) the prevalence and impact of precipitating stressors on in-hospital and long-term CV events. Secondary Objectives:
2. To evaluate the in-hospital and long-term outcomes of conservative therapy and revascularization in patients with NA-SCAD.
3. To evaluate the presenting angiographic patterns of NA-SCAD.
4. To assess the incidence of spontaneous arterial healing with conservative medical therapy alone in NA-SCAD patients undergoing repeat angiography.

Hypotheses:

1. We hypothesize that NA-SCAD patients have a high risk of long-term recurrent CV events and FMD, as the most frequently observed predisposing condition confers lower subsequent risk compared to other arteriopathies, such as peripartum SCAD, with regards to CV outcomes. We hypothesize that precipitating stressors are common preceding the SCAD event in >50% of cases.
2. We hypothesize that NA-SCAD patients have a high risk of long-term CV events, and that patients who undergo revascularization have worse CV outcomes.
3. We hypothesize that the most common angiographic NA-SCAD pattern is diffuse stenosis.
4. We hypothesize that conservative medical therapy is associated with high rates of spontaneous healing.

Methodology:

Prospective Canadian observational cohort study enrolling 750 consecutive patients presenting with MI (NSTEMI or STEMI) due to NA-SCAD. Both women and men will be included. Rigorous coronary angiographic criteria with supplementary intracoronary imaging (reviewed by core laboratory) will be used for SCAD diagnosis. Detailed baseline demographics, targeted history for predisposing and precipitating factors, and screening laboratory tests will be performed. Patients will be prospectively followed for 3 years for CV events.

Significance:

This study will have significant impacts on the diagnosis, investigation, and management of NA-SCAD. Our diagnostic algorithm will help establish guidelines on SCAD diagnosis on coronary angiogram, which is currently elusive. Our rigorous clinical and laboratory screening will elucidate the prevalence of predisposing arteriopathies, which will help establish guidelines on investigation of SCAD patients. Knowledge of CV outcomes and natural history of NA-SCAD, especially stratified to predisposing arteriopathies, will establish prognosis, risk stratification, and management guidelines.

Knowledge Translation:

Our results will be disseminated to clinicians and patients through publications in scientific journals, physician scientific presentations, Healthy Heart Programs, patient educational sessions, educational website, and public media. Results from this study will help establish national and international guidelines on the diagnosis, investigation and management of NA-SCAD.