The culprit coronary artery lesion

PET measurement of the coronary flow reserve and microcirculatory function

This review article discusses some of the potentially beneficial effects of calcium antagonists on the coronary microcirculation. These include their vasodilating action on coronary resistance vessels as well as their effects on extravascular resistance (i.e. intramyocardial pressure). Examples are presented of how the non-invasive measurement of myocardial blood flow and flow reserve by means of positron emission tomography (PET) can contribute to the understanding of the effects of drug treatment on the coronary microcirculation. The action of calcium antagonists on the coronary microcirculation can contribute to explain the efficacy of these drugs against ischemia and ischemia-reperfusion damage.

Predictors for waiting time for coronary angioplasty in a high risk population

Objective--To describe the clinical and non-clinical factors which influence the waiting time from initial angiography to angioplasty. Design--Follow up of a random sample of 106 patients undergoing their first coronary angiography for whom a decision to revascularise by percutaneous transluminal angioplasty was made in 1991. The period between the date of angiography and the date of angioplasty and various clinical characteristics of patients were retrieved from medical notes in mid 1993. Patients were sampled from those investigated in the two Northern Ireland catheterisation laboratories in Belfast, which provide services for the whole of the province (population 1.5 million). Main measures--The dependent variable was the period between initial angiography and angioplasty, and the independent variables included age, sex, distance from cardiac catheterisation centre, referral source, characteristics of the clinical history, severity of angina, and anatomical extent of disease. Cox's proportional hazards analysis was used to derive a relative hazard, expressing the relative chances of revascularisation occurring at any time during follow up. Results--Of the 106 patients studied, 93 had had percutaneous transluminal angioplasty at follow up. The most important predictors of waiting time were the presence of severe angina (relative hazards 3.1(95 % confidence interval (95% CI) 1.4-6.8) and 2.7(1.2-6.2) for Canadian Cardiovascular grades III and IV v angina grade I angina), a recent history of myocardial infarction (relative hazard, 2.5(1.3-4.8), and whether or not the patient was economically active (relative hazard 0.6(0.4-1.0) for economically inactive v active patients). Although there was also an association with the relative deprivation of the area of residence of the patient it had no clear linear trend. Conclusions--Although waiting time for percutaneous transluminal angioplasty was predictably related to the patient's clinical presentation, demographic factors may also be important in determining access to intervention. These factors clearly merit further study; ultimately, the evaluation of equity in a waiting time distribution may more properly be a societal rather than a clinical judgment.

Are the economically active more deserving?

OBJECTIVE

To investigate the possibility of an association between the duration of medical treatment before coronary angiography and demographic and non-clinical factors.

DESIGN

A systematic review of a random sample of 500 patients undergoing their first angiographic assessment.

SUBJECTS

500 cases were selected randomly from patients investigated in 1991 at the two catheterisation centres in Northern Ireland.

MAIN OUTCOME MEASURES

The duration of medical management before angiography.

RESULTS

346 had elective and 154 urgent catheterisation. The duration of medical management was adjusted for both case mix (age at onset, body mass index, angina grade, history of myocardial infarction, history of hypertension, diabetes or hyperlipidaemia, treatment intensity) and other demographic variables (sex, smoking status, an indicator of "deprivation", and distance of the patient's area of residence from the hospital). After this adjustment the mean duration of medical management before angiography was twice as long for economically inactive patients as for those who were economically active. In a multiple regression, the relevant beta coefficient was 0.44 (95% confidence interval 0.33 to 0.58, P < 0.0001).

CONCLUSIONS

These results suggest that, in making discretionary decisions about when to refer patients with angina for revascularisation assessment, doctors may be influenced by non-clinical factors unrelated to disease severity.

Expanding access to coronary artery bypass surgery: who stands to gain?

OBJECTIVE

To determine the perceptions of general practitioners (GPs) about the benefits of coronary artery bypass surgery, in terms of gains in life expectancy, for different groups of patients.

DESIGN

A questionnaire survey of all GPs in Northern Ireland.

SETTING

A survey conducted collaboratively by the departments of public health medicine in each of the four health boards in the province, serving a total population of 1.5 million.

MAIN OUTCOME MEASURES

The median and mean gain in life expectancy perceived by groups of doctors for smoking and non-smoking male and female 55 year old patients. The percentage of 50 year old and 70 year old non-smoking patients considered likely to have their lives extended with bypass surgery. Differences were assessed using the Mann-Whitney U test for unpaired samples and the Wilcoxon signed rank tests for paired.

RESULTS

541 GPs replied (response rate 56%). The median (and mean) perceived gain in life expectancy after cardiac surgery for non-smoking 55 year old subjects was 120 (104) months for men and 120 (112) months for women (z = 6.42; P < 0.0001; Wilcoxon signed rank test). For male and female smokers of the same age, the perceived gains were 48 (47) and 60 (52) months respectively (z = 6.72; P < 0.0001; Wilcoxon signed ranks test), both figures being significantly different than for non-smokers. The median (and mean) percentage of patients that the doctors considered would have their lives extended by bypass surgery was 70 (64) of every 100 "young" patients and 40 (42) of every 100 "old" patients, (z = 16.2; P < 0.0001).

CONCLUSIONS

These results point to a significant overestimation of the benefits of coronary artery bypass surgery by GPs in Northern Ireland and to a need to develop guidelines for referral.

Is choice of general practitioner important for patients having coronary artery investigations?

OBJECTIVE

To determine whether particular sociodemographic characteristics of patients with stable angina affected their general practitioners' (GPs') decisions to refer them for revascularisation assessment.

DESIGN

Postal questionnaire survey.

SETTING

Collaborative survey by the departments of public health medicine in each of the four health boards in Northern Ireland, serving a total population of 1.5 million.

SUBJECTS

All (962) GPs.

MAIN MEASURES

The relation between GPs' referral decisions and patients' age, sex, employment status, home circumstances, smoking habits, and obesity.

RESULTS

541 GPs replied (response rate 56%). Most were "neutral" towards a patient's sex (428, 79%), weight (331, 61%), smoking habit (302, 56%), employment status (431, 80%), and home circumstances (408, 75%) in making decisions about referral. In assigning priority for surgery most were neutral towards the patient's sex (459, 85%), employment status (378, 70%), and home circumstances (295, 55%). However, most GPs (518, 95%) said that younger patients were more likely to be referred, and a significant minority were less likely to refer patients who smoked (202, 37%) and obese patients (175, 32%) and more likely to refer employed patients (97, 18%) and those with dependents (117, 22%) (compared with patients with otherwise comparable clinical characteristics); these views paralleled the priority which GPs assigned these groups. The stated likelihood of referral of young patients was independent of the GPs' belief in ability to benefit from revascularisation, but propensity to refer and perception of benefit were significantly associated for all other patient characteristics.

CONCLUSION

GPs' weighting of certain characteristics in reaching decisions about referral for angiography is not uniform and may contribute to unequal access to revascularisation services for certain patient groups.

Referrals for coronary angiography in a high risk population

OBJECTIVES

To examine variations in referral for coronary angiography within Northern Ireland and relate these to local death rates from coronary artery disease (ICD rubrics 410-414).

DESIGN

A descriptive retrospective analysis of aggregate hospital activity data for 1979-88 and corresponding mortality rates in the local population.

SETTING

Two regional referral hospitals and 26 local district council areas.

PATIENTS

5173 patients aged 35-74 years with an underlying diagnosis of ischaemic heart disease, whose records contained complete information on their age, sex, and home address.

MAIN MEASURES

Age-standardised angiography rates and corresponding standardised death rates derived from the registrar general's reports.

RESULTS

Among the 26 constituent district council areas there was significant heterogeneity in the angiography rates, ranging from 62 to 335/100,000 in men and from 7 to 62/100,000 in women (likelihood ratio statistic 856 and 359 respectively). There was no significant association between these angiography rates and the local death rates from ischaemic heart disease.

CONCLUSION

The results suggest a non-uniform threshold for referral for angiography.

IMPLICATIONS

Clinicians need to examine the appropriate indications for referral for invasive investigation.