Cardiovascular Journal of Africa: Vol 26 No 2 (March/April 2015)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 2, March/April 2015

AFRICA

The diagnosis of FMD depends almost exclusively on the

angiographic appearances of the affected vessel/s. The ‘string

of beads’ deformity of the arterial lumen is typical, but luminal

narrowing, arterial tortuosity with kinks, coils or loops, or

aneurysm formation may be present.

Phenotypic differences

have been described between patients with multifocal (‘string of

beads’) and unifocal (a single isolated stenosis) lesions.

Despite the abnormal vascular architecture, the functional

significance of the lesions of FMD cannot be established

from the angiogram. Intravascular ultrasound imaging or

measurement of the pressure gradient across the lesions is more

valuable.

The ‘string of beads’ deformity is seen infrequently in

coronary FMD. More commonly, the coronary vessels may

appear normal, demonstrate dissection with either an intimal

tear or an intramural haematoma, an abrupt reduction in vessel

calibre with a long segment narrowing distally, or an unusual

tortuosity.

Multivessel involvement of the coronary arteries

has been described. Diffuse and typically smooth stenoses may

be confused with atherosclerotic coronary artery disease.

The

diagnosis of coronary FMD relies upon the demonstration of

the typical angiographic features in an extracardiac vascular

territory.

There is a strong association between FMD and spontaneous

coronary artery dissection (SCAD). SCAD is present in 10%

of women under the age of 55 years who present with an ACS.

Women with SCAD are younger and have fewer risk factors for

atherosclerotic coronary disease than those without, and 78%

have features of FMD.

In a series reporting on 50 patients with

SCAD, 98% were women. The average age was 51.0

9.6 years.

Definite evidence of FMD was found in 86% of patients.

A third study found that 60–70% of SCAD patients had

extracoronary vascular abnormalities.

The onset of SCAD

has been associated with emotional distress, isometric exercise

and the post-partum state.

2,14

SCAD presents as an ACS,

either as non-ST-segment elevation (70%) or ST-segment

elevation myocardial infarction (30%).

It has been proposed

that intravascular imaging be strongly considered in patients

suspected of SCAD.

Optical coherence tomography reveals a

thicker-than-normal dissection flap consisting of both intima

and media.

SCAD may recur in as many as one-sixth of patients, rising to

20% in women after a pregnancy. Although some have regarded

the post-ACS course as benign,

a subgroup analysis of the

GENESIS PRAXY study found that SCAD doubled the death

and rehospitalisation rates at 12 months.

The 10-year composite

rate of death, heart failure, myocardial infarction and recurrent

SCAD has been estimated at 47%.

Once the close association between FMD and SCAD was

appreciated, the patient’s coronary angiogram was reviewed

meticulously. A frame-by-frame analysis of various views

revealed the presence of a previously undetected long dissection

within the circumflex, which was only fleetingly visible when the

angiogram was viewed in ciné mode (Fig. 4).

The frequent misdiagnosis of SCAD from coronary

angiography has been noted previously. The dissection may

be missed or incorrectly interpreted as due to atherosclerosis.

While intravascular ultrasound (IVUS) and optical coherence

tomography (OCT) vividly demonstrate the presence of coronary

dissection, SCAD may be overlooked in most patients when

depending solely on the ciné-angiogram for diagnosis.

15,16

There is no specific therapy for coronary FMD nor is

there consensus on the treatment of SCAD. SCAD heals

spontaneously over time. In cases in which late follow-up

angiography has been performed, the coronary vessels have

been seen to resume a normal appearance.

Acute intervention

with balloon angioplasty or stenting of the affected segment

carries the risk of extruding thrombus into the false lumen and

propagating the dissection to unaffected arterial segments.

The

technical failure rate with percutaneous intervention in SCAD

is 35%.

In this setting, IVUS and/or OCT may play a valuable

role in identifying the entry tear and allowing for highly

localised stenting to seal the intima.

However, given the

fragility of the vessel wall in SCAD, caution is advisable when

using intravascular imaging techniques. It is recommended that

coronary intervention should be reserved for only those patients

with reduced coronary flow or ongoing ischaemia. As our

patient’s chest pain settled completely, as the ECG returned to

normal and as there was unobstructed coronary flow, stenting

of her dissection was deemed inappropriate.

Fibrinolysis and glycoprotein IIb/IIIa inhibitors also should

be avoided during the acute presentation. In the absence of

clinical trials, it is recommended that the patient receive dual

antiplatelet therapy to maintain vessel patency, beta-blockade

to diminish vascular wall stress, and an angiotensin converting

enzyme inhibitor or angiotensin receptor blocker should the

treatment of hypertension be needed. Statin treatment has no

proven role in the management of FMD. Smoking should be

avoided as it may aggravate FMD.

Oestrogen therapy also

should be avoided unless there is a strong indication to use it.

Women of child-bearing age who experience an ACS due

to SCAD require an accurate diagnosis and counselling about

the risk of future pregnancy.

Expert opinion is that strenuous

exertion should be avoided. The patient with SCAD should be

investigated for the presence of FMD in the other commonly

affected vascular territories, namely renal, carotid, mesenteric

and iliac arteries. Treatment of these lesions is indicated when

accompanied by symptoms.

Conclusion

SCAD is a not-infrequent cause of acute coronary syndrome

in women under the age of 55 years. The close association

between SCAD and FMD strongly suggests that they are

causally linked. Both FMD and SCAD are underdiagnosed

and may elude detection during coronary angiography. For this

reason, intravascular imaging with OCT could be considered

when a diagnosis of SCAD seems likely. Despite the absence

of randomised clinical trial evidence to guide management,

the expert recommendations regarding the pharmaceutical and

interventional treatment of SCAD differ importantly from the

guidelines applicable to patients with the usual causes of ACS.

Patients with SCAD should be investigated for the presence of

FMD in other vascular territories. Conversely, a high index of

suspicion of SCAD is warranted in patients with known FMD

who present with ACS.

Mr Quinton Barber of AstraZeneca is thanked for supplying certain of the

references quoted.