Exercise myocardial perfusion scintigraphy is useful for evaluating myocardial ischemia even in the elderly

Contribution of Age-Related Microvascular Dysfunction to Abnormal Coronary: Hemodynamics in Patients With Ischemic Heart Disease

OBJECTIVES

This study sought to investigate the contribution of age-related microcirculatory dysfunction to abnormal coronary hemodynamics in patients with coronary atherosclerosis.

BACKGROUND

Impairment in myocardial blood supply in patients with coronary atherosclerosis can be accentuated due to age-related changes in microcirculatory function.

METHODS

Intracoronary pressure and flow were measured with the Doppler technique in 299 vessels (228 patients), and the thermodilution technique in 120 vessels (99 patients). In 172 patients, Doppler measurements were also performed in unobstructed vessels. Associations of coronary hemodynamics with aging were studied in both the stenosed and unobstructed arteries.

RESULTS

Aging was associated with a progressive increase in minimal microvascular resistance and a progressive decrease in hyperemic flow in both obstructed and nonobstructed coronary arteries. As such, coronary flow reserve decreased with advancing age. Epicardial stenosis severity assessed by resting Pd/Pa, basal stenosis resistance index, and hyperemic stenosis resistance index was equivalent across age groups. By contrast, fractional flow reserve increased with advancing age. Consequently, the adjusted risk of a fractional flow reserve/coronary flow reserve pattern reflective of concomitant focal epicardial and diffuse or microvascular disease (relative risk: 1.6; 95% confidence interval: 1.1 to 2.3; p = 0.017) increased with advancing age, whilst the adjusted risk of a fractional flow reserve/coronary flow reserve pattern reflective of non-flow-limiting stenosis with a healthy microcirculation decreased (relative risk: 0.7; 95% CI: 0.5 to 1.0; p = 0.022).

CONCLUSIONS

Aging is associated with progressive pan-myocardial impairment of coronary vasodilatory capacity due to an increase in minimal microvascular resistance. Concomitant aging-related impairment in microvascular function impacts the pathophysiology of ischemic heart disease in the individual patient and is not adequately identified by hyperemic coronary pressure measurements alone.

The Prognostic Value of Vasodilator Myocardial Perfusion Imaging in Octogenarians

The ability of single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to stratify risk in octogenarians is poorly defined. The authors identified 439 octogenarians who underwent vasodilator SPECT MPI between 1994 and 2000. Over a mean 2.5 years of follow-up, moderate and large stress defects were associated with increased crude mortality (normal: 24.5%, small defect: 21.9%, moderate or large stress defect: 41.4%, p for trend < 0.001). The degree of defect reversibility was also strongly associated with increased mortality (normal: 24.5%, no reversibility: 22.0%, small reversible defect: 36.5%, moderate or large reversible defect: 50.0%, p for trend < 0.001). In multivariable analysis, stress defects were the strongest predictor of mortality (hazard ratio, 2.39; 95% confidence interval, 1.56-3.65). The mortality of octogenarians with moderate or large perfusion defects is nearly double that of patients with normal or mildly abnormal MPI. Appropriately selected octogenarians with abnormal vasodilator SPECT imaging may benefit from more aggressive management of their cardiac disease.

Myocardial perfusion scintigraphy: the evidence

This review summarises the evidence for the role of myocardial perfusion scintigraphy (MPS) in patients with known or suspected coronary artery disease. It is the product of a consensus conference organised by the British Cardiac Society, the British Nuclear Cardiology Society and the British Nuclear Medicine Society and is endorsed by the Royal College of Physicians of London and the Royal College of Radiologists. It was used to inform the UK National Institute of Clinical Excellence in their appraisal of MPS in patients with chest pain and myocardial infarction. MPS is a well-established, non-invasive imaging technique with a large body of evidence to support its effectiveness in the diagnosis and management of angina and myocardial infarction. It is more accurate than the exercise ECG in detecting myocardial ischaemia and it is the single most powerful technique for predicting future coronary events. The high diagnostic accuracy of MPS allows reliable risk stratification and guides the selection of patients for further interventions, such as revascularisation. This in turn allows more appropriate utilisation of resources, with the potential for both improved clinical outcomes and greater cost-effectiveness. Evidence from modelling and observational studies supports the enhanced cost-effectiveness associated with MPS use. In patients presenting with stable or acute chest pain, strategies of investigation involving MPS are more cost-effective than those not using the technique. MPS also has particular advantages over alternative techniques in the management of a number of patient subgroups, including women, the elderly and those with diabetes, and its use will have a favourable impact on cost-effectiveness in these groups. MPS is already an integral part of many clinical guidelines for the investigation and management of angina and myocardial infarction. However, the technique is underutilised in the UK, as judged by the inappropriately long waiting times and by comparison with the numbers of revascularisations and coronary angiograms performed. Furthermore, MPS activity levels in this country fall far short of those in comparable European countries, with about half as many scans being undertaken per year. Currently, the number of MPS studies performed annually in the UK is 1,200/million population/year. We estimate the real need to be 4,000/million/year. The current average waiting time is 20 weeks and we recommend that clinically appropriate upper limits of waiting time are 6 weeks for routine studies and 1 week for urgent studies.