Myocardial revascularisation is appropriate when the expected benefits- survival, relief of symptoms, and improvement of quality of life- exceed the potential negative consequences of the procedure. Risk assessment is therefore crucial in contemporary clinical practice, and should hinge on developed risk scores to predict mortality: SYNTAX for percutaneous coronary interventions (PCI), EuroSCORE for percutaneous and surgical interventions, the Grace Score for treatment revascularisation in non-ST-segment elevation acute coronary syndromes and on registries: the National Cardiovascular Database Registry (NCDR CathPCI) for PCI and the Society of Thoracic Surgeons (STS) for coronary bypass graft (CABG) operations.
Patients should also take an active role in the decision-making process, therefore information is mandatory. This strategy has been shown to improve outcomes (1). A multidisciplinary team, the "Heart Team" should meet and discuss each patient's characteristics to develop an objective decision process involving consideration for sex, race, availability, technical skills, local results, referral patterns, and patient preference. In order to have enough time for this process, revascularisation should be planned within a lapse of time, unstable patients excluded (see table 1).
Table 1.Potential indications for ad hoc percutaneous coronary intervention and revascularisation at an interval.
I - Pre-intervention diagnosis and imaging
Exercise testing and cardiac imaging can confirm the diagnosis of coronary artery disease (CAD), document ischaemia, stratify patient’s risk, detect myocardial viability, and help determine optimal treatment options. Nevertheless, the risks associated with the cardiac imaging test itself- cumulative ionising radiation, contrast agents, must be taken into account.
Multidetector computed tomography (MDCT) has shown high negative predictive values and is an excellent diagnostic tool to exclude significant CAD. Positive predictive values are only moderate, so in cases of high calcium score or significant stenosis detected with MDCT, invasive coronary angiography should be indicated. Magnetic resonance imaging (MRI) coronary angiography has lower success rates and is less accurate than MDCT for the detection of CAD.
Stress imaging techniques are superior to conventional exercise ECG testing. Besides being able to localise areas of ischaemia, stress imaging provides diagnostic information in the presence of resting ECG abnormalities or in patients unable to exercise. Stress echocardiography, perfusion scintigraphy and cardiovascular MRI imaging all share similar sensitivity and specificity and are preferred in patients with previous PCI or CABG. The presence of ischaemia predicts cardiovascular events in patients with angiographically-detected intermediate coronary lesions.
II. Revascularisation for stable CAD
Revascularisation should be considered in patients whose symptoms persist despite optimal medical treatment (OMT) and/or to improve prognosis. Symptomatic patients with no or little evidence of ischaemia do not get prognostic benefit from revascularisation, while asymptomatic patients with a significant ischaemic burden do (see Table 2).
Table 2. Indications for revascularisation in patients with stable angina or silent ischaemia (1).
When comparing the efficacy of PCI vs. optimal medical treatment (OMT), most meta-analyses show no mortality benefit with OMT and a reduced need for repeat revascularisation, both findings working in favour of PCI. Two meta-analyses have reported reduced mortality with PCI in a study comparying PCI vs. OMT (HR 0,82, 95% confidence interval: 0,68-0,99) (2).
Regarding which stents to use, several meta-analyses and randomised clinical trials comparing DES with bare-metal stents (BMS) reported similar rates of death and non-fatal MI however there was a significant reduction in the need for subsequent target vessel revascularisation (TVR) with DES, and some observational studies have shown reduction in mortality associated with their use as well. Table 3 summarises the indications for deciding whether PCI or CABG should be indicated for revascularisation. The SYNTAX Trial (3) included 1800 patients with left main (LM) and/or three-vessel CAD randomised to PCI or CABG and showed that patients had less major adverse cardiovascular events (MACE) with CABG (16,3% vs. 23,4%; p< 0,001) only the third lowest-scoring SYNTAX score patients (< 23) showed no significant differences between PCI and CABG.
Table 3. Indications for coronary artery bypass grafting vs. percutaneous coronary intervention in stable patients with lesions suitable for both procedures and low predicted surgical mortality (1). Find SYNTAX score here.
III. Revascularisation in non-ST-Segment elevation coronary syndromes (NSTE-ACS)
The goals of revascularisation are symptom relief and improvement of prognosis. As NSTE-ACS patients constitute a highly heterogeneous group, risk stratification should help to determine strategy. ESC Guidelines for NSTE-ACS recommend using th GRACE risk score to guide clinical management (4,5). Troponin elevation and ST depression at baseline appear to be the most powerful individual predictors of benefit from invasive treatment. Randomised clinical trials have demonstrated that early invasive strategy reduces ischaemic endpoints by lowering recurrent severe ischaemia and lessening the clinical need for rehospitalisation and revascularisation (table 4). Additionaly, the number of ischaemic events as well as bleeding complications tend to be lower and hospital stays shorter with early invasive strategy.
Table 4. Recommendations for revascularisation in non-ST-segment elevation acute coronary syndromes (1). Find GRACE score here.
Predictors of high thrombotic risk or high-risk for progression to myocardial infarction, which are an indication for coronary angiography are (1,6):
- Ongoing or recurrent ischaemia
- Dynamic spontaneous ST changes (>0.1 mV depression or transient elevation)
- Deep ST depression in anterior leads V2–V4 indicating ongoing posterior transmural ischaemia
- Haemodynamic instability
- Major ventricular arrhythmia
In lower-risk patients, revascularisation can be delayed without increased risk but should be performed during the hospital stay, preferably within 72 hours of admission. Although women and the elderly may be at higher risk of bleeding, they should not be treated any differently including within the context of clinical trials.
IV. Revascularisation in STE-ACS
Compared to fibrinolysis, primary PCI performed within the first 6-12 hours after symptom onset has yielded more effective restoration of vessel patency, less re-occlusion, improved residual LV function and better clinical outcome. It is essential to minimise all delays. If the expected delay is less than 2 hours, patients admitted to a non-PCI centre should receive fibrinolysis and then be transferred to a PCI-capable centre. In cases of persistent ST-segment elevation following fibrinolysis (more than a half of the maximal initial elevation in the worst ECG lead) and/or persistent ischaemic chest pain, rescue angioplasty should be considered. In cases of successful fibrinolysis, patients may be referred for PCI within 24 hours (Table 5) (7).
In patients presenting more than 3 days after onset of the acute event with a fully developed Q-wave MI, revascularisation may be performed in those with recurrent angina and/or documented ischaemia and viability.
Echocardiography should always be performed in the setting of acute heart failure to asses LV function and to rule out life-threatening mechanical complications that may require surgery (i.e mitral regurgitation, ventricular septal defect, free wall rupture or cardiac tamponade). In those patients complete revascularisation is recommended, with PCI performed in all critically stenosed large epical coronary arteries. In the presence of haemodynamic impairment, intra-aortic balloon pump (IABP) is recommended.
Cardiogenic shock is the leading cause of in-hospital death for MI patients.
Table 5. ST-segment elevation myocardial infarction patient pathway describing pre- and in-hospital management and reperfusion strategies within 12 hours of first medical contact.