Ahora es un poco mas dificil.

Fig 3Two images from the computed tomography coronary angiogram.


Fig 1 Exercise tolerance electrocardiogram

A 43 year old Asian woman was referred to the cardiology outpatient clinic with recurrent episodes of chest pain, which she had experienced since early childhood. She described the chest pain as a central tightness that occurred when she exercised. She had recently developed paroxysms of fast regular palpitations, which had prompted her referral. Her only known coronary risk factor was a family history of premature coronary disease. Physical examination was unremarkable and her blood pressure was 110/56 mm Hg. Routine haematology and biochemistry tests, including her thyroid stimulating hormone concentration, were all within normal limits. A 12 lead electrocardiogram (ECG) showed normal sinus rhythm. A 24 hour Holter ECG showed sinus rhythm with occasional supraventricular ectopic beats and no suggestions of any ST segment change (no diary entries). Chest radiography, echocardiography, and pulmonary function tests were unremarkable. She went on to have a Bruce protocol exercise tolerance test. Her ECG at peak exercise (eight minutes) is shown (fig 1).

Questions

1 What does the exercise tolerance ECG show?

2 What are the possible underlying causes of the ECG changes?

3 Computed tomography coronary angiography showed an anomalous right coronary artery emanating from the left coronary sinus. Why is this a problem and how does it explain the ischaemia?

4 What further investigations should be considered?

5 How might this condition be managed?

Answers

1 What does the exercise tolerance ECG show?

Down-sloping ST segment depression in the lateral leads (V4-V6), which is suggestive of myocardial ischaemia (fig 2).


Fig 2 Exercise tolerance electrocardiogram showing ST segment depression in leads V4, V5, and V6 (arrows)

Down-sloping and planar (horizontal) ST segment depression are more specific for underlying ischaemia than up-sloping ST depression, which can be a normal phenomenon during exercise. The depth of ST depression (1.5 mm in this case) is also diagnostically important, with deeper depression more likely than shallow depression to reflect ischaemia. Unlike ST elevation, ST segment depression does not reliably indicate the area of myocardium or artery giving rise to the ischaemia.

2 What are the possible underlying causes of the ECG changes?

Although underlying causes include atherosclerosis, coronary spasm, coronary microvasculature dysfunction, and external compression of a coronary artery, younger women have a higher false positive rate with this test and so the results should be interpreted with caution.

3 Computed tomography coronary angiography showed an anomalous right coronary artery emanating from the left coronary sinus. Why is this a problem and how does it explain the ischaemia?

Fig 3 Two images from the computed tomography coronary angiogram [above]. The right coronary artery (black arrow) is seen to emerge from the left coronary sinus where it appears to be compressed by the aorta (asterisk) and pulmonary artery (hash sign) before entering the atrioventricular groove. The left main stem is also seen (white arrow). The image on the left is a two dimensional slice at the level of the aortic root and the image on the right is a three dimensional reconstruction. The pulmonary artery is not seen on the three dimensional reconstruction.

Short answer

When a coronary artery emerges from the wrong side of the aorta it often has to course between the aorta and pulmonary artery to reach its normal territory. The artery is then susceptible to compression by the great vessels, especially during hyperdynamic states such as physical exertion.

4 What further investigations should be considered?

Short answer

Functional cardiac imaging, such as stress echocardiography, radioisotope perfusion scanning, or stress magnetic resonance imaging, will determine the presence (or absence) and location of ischaemia, which is vital in determining appropriate management.

5 How might this condition be managed?

Long answer

Anomalous coronary origin from the wrong sinus of Valsalva is the most common coronary anomaly and may demonstrate a familial tendency. Although this anomaly is usually asymptomatic, symptoms can include angina pectoris, syncope, sudden cardiac death, and malignant arrhythmia. The most worrying feature is the association with sudden cardiac death, which is thought to result from ventricular arrhythmias triggered by ischaemia. Sudden cardiac death is more common in patients with anomalies that affect the left coronary system than the right. Worryingly, most patients remain asymptomatic before sudden cardiac death. Features such as the artery coursing between the aorta and pulmonary artery, a slit-like orifice, and an intramural course are thought to be important risk factors for sudden cardiac death. Management remains controversial because, understandably, few long term data are available. However, it is currently accepted that this condition should be surgically repaired if the left anterior descending coronary artery courses between the aorta and the pulmonary artery, regardless of evidence of ischaemia, or if the right coronary artery courses between the great vessels with documented evidence of ischaemia. The nature of the revascularisation is variable, but options include ostioplasty, bypass grafting, reimplantation, unroofing of intramural coronary segment, and percutaneous coronary intervention with stenting.

Patient outcome

This patient had evidence of ischaemia at a low threshold in the territory of the right coronary artery. The case was discussed in a joint cardiology and cardiothoracic surgery multidisciplinary team meeting. The final decision was to refer for coronary artery bypass grafting to the right coronary artery.

[Link to free BMJ article for full text, images, answers, and references]

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