What is it?
SCAD is an uncommon but potentially dangerous cause for heart attacks in young patients and especially young women (less than 50 years of age).
Most heart attacks occur because of a blockage in the lumen of a coronary artery. This is usually because of build-up of atherosclerotic plaque over a number of years and this is why heart attacks are more common in the elderly.
In SCAD however, the problem is in the wall of the coronary artery. For some reason, bleeding occurs within the wall (in the absence of any precipitating trauma) and the layers of the wall become separated to accommodate the bleeding. This in turn has the effect of reducing the size of the lumen or even squeezing the lumen shut thereby causing a blockage and thereby leading to a heart attack. If the amount of heart muscle deprived of blood is large, then the resulting heart attack can even lead to heart failure, dangerous heart rhythm disturbances or even sudden death.
Who gets it?
Typically, it affects women below the age of 50 years of age. Women outnumber men by a ratio of 9:1
SCAD is considered a rare cause of heart attacks. It probably is responsible for about 4% of all heart attacks. In women aged 50 or less it probably accounts of 25-35% of all heart attacks. The proportion is even higher in pregnant women.
Why does it happen?
We don’t know for sure. It is believed that especially in pregnancy, hormonal changes (in the third trimester and during childbirth and even in the immediate period after delivery can make the arterial walls more vulnerable and weak. What we don’t know for sure is whether it is just about the pregnancy or whether the patient themselves have an underlying propensity to start off with. What we do know is that people with very tortuous coronary arteries seem to be more predisposed to SCAD.
Several conditions can cause an underlying propensity to a weaker coronary artery walls.
1) Fibromuscular dysplasia (about 60-70% of patients with SCAD are found to have extra coronary fibromuscular dysplasia and 14% of those patients have intracranial aneursyms)
2) Connective tissue disease (ehlers danlos type IV; Marfans syndrome)
3) Recurrent previous pregnancies
4) Hormonal therapy
5) Systemic inflammatory diseases
Exposure to a significant stressor in a patient with an underlying propensity can then lead to SCAD.
Common stressors include:
1) Emotional stress
2) Extreme physical stress (exercise; labour; delivery)
3) The Valsalva manoeuvre (excessive straining)
4) Drug abuse
How does it present:
This can be variable and very dependent on the degree of flow limitation and extent of dissection.
It may be asymptomatic or in the most extreme cases, present with sudden death.
Most patients will present with severe crushing chest discomfort, nausea, clamminess, breathlessness and dizziness.
What investigations are needed to confirm the diagnosis?
The ECG may show signs of a heart attack and the blood tests associated with heart muscle damage may be elevated. However this only points to the diagnosis of a heart attack and not of SCAD per se. The definitive test is a coronary angiogram to delineate the heart arteries. There are 3 patterns seen which point to a diagnosis of SCAD.
1) Type 1: This pattern is seen in 25% of cases of SCAD. When they inject dye into the coronaries, the dye is seen entering and staining the wall of the coronary artery suggesting that there is an entry point from the true lumen of the coronary artery into a false lumen
2) Type 2: This occurs in about 70% of SCAD cases. Here the appearance is of a smooth diffuse narrowing of the artery rather than the focal irregular narrowings associated with atherosclerotic plaque
3) Type 3: This occurs in 5% of cases and can be more focal and can be difficult to distinguish from atherosclerosis. In this setting, more sophisticated imaging such optical coherence tomography can help clarify.
What is the treatment for SCAD?
Once the diagnosis is made the first line therapy is conservative management and close monitoring for 3-5 days. Stenting is generally considered a bad idea because of the risk of causing additional trauma and propagating the dissection even further. In such a setting stenting is only 60% effective. There are a few cases in which stenting may be considered. These include if the dissection is happening in a particularly large blood vessel and threatening a large part of the heart or if there are more than one blood vessels affected or even if the patient is clinically very unstable.
What other tests should be done?
All patients with SCAD should have screening of all other blood vessels including kidney, iliac and cerebral blood vessels. Because fibromuscular dysplasia is often a common underlying predisposition, patients should be screened for this condition by either CT angiography or MR angiography.
What long term treatment should be given?
Clopidogrel for a year
Statins if there is evidence of excessively high cholesterol
ACE inhibitors and beta blockers if there is associated significant heart muscle damage causing a reduced function of the heart
What is the prognosis?
In studies in patients who have had SCAD and repeat angiographies, the lesions have healed in 70-97%
In patients with SCAD, 4.5% suffer a heart attack in hospital
17% suffer a major cardiac event in the next 2 years
13% have a recurrence of SCAD
Is it safe to get pregnant if I have had SCAD in the past?
Given the concerns for possible recurrent SCAD on re-exposure to the stresses during pregnancy, many clinicians advise against subsequent pregnancies in SCAD survivors. This potentially life changing advice is unfortunately not based on a robust evidence base. The only evidence is from a tiny study that followed 8 SCAD survivors who had become pregnant again for 36 months. In this tiny group of patients, 1 patient experienced recurrent SCAD after delivering.
Patients who do want to get pregnant after surviving SCAD should be managed in a tertiary centre asap and be followed up carefully by a team which includes cardiologists who have expertise in SCAD, obstetricians, obstetric anaesthetists and maternal fetal medicine specialists. The things to pay particular attention during pregnancy and especially delivery are really good pain control with early epidural placement, delivering in the left lateral decubitus position, treatment of high blood pressure and minimising maternal effort during delivery. Where possible vaginal delivery is still the preferred form of delivery.
Can I exercise after SCAD?
Patients should join an exercise rehabilitation program to aid their recovery. In one such program patients were encouraged to keep the heart rate no higher at 50-70% of their maximum predicted heart rate and to keep their systolic blood pressure less than 130mmHg. Women were encouraged to lift no more than 20-30 pounds and men, no more than 50 pounds. Such a rehab program was shown to be both safe and beneficial in SCAD survivors.
Useful links and references:
SCAD; Spontaneous coronary artery dissection; heart attacks in pregnancy