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Eur J Cardiothorac Surg 2001;19:260-265
© 2001 Elsevier Science NL
a Department of Cardiology, St. Antonius Hospital, Nieuwegein, The Netherlands
b Department of Clinical Epidemiology and Biostatistics, Academic Medical Centre – University of Amsterdam, Amsterdam, The Netherlands
Received 25 July 2000; received in revised form 20 November 2000; accepted 30 December 2000.
Corresponding author. Department of Cardiology, St. Antonius Hospital, P.O. Box 2500, 3430 EM, Nieuwegein, The Netherlands. Tel.: +31-30-6092278; fax: +31-30-6092274
e-mail: koomen.em{at}net.hcc.nl
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Abstract |
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 Top Abstract 1. Introduction2. Methods3. Results4. DiscussionReferences |
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Key Words: Waiting lists • Coronary artery bypass graft surgery • Morbidity • Mortality • Triage
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1. Introduction |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionReferences |
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The nature of coronary artery disease implies that critical events may occur at any moment during the whole chain of waiting, from the first anginal complaint until the very day of surgery. It is known that some patients are at higher risk for these complications than others. Therefore, triage, a selection and ranking system based on informal consensus, including symptoms, coronary anatomy and risk profile, has been used to reduce the number of critical events. However, reliable determinants for risk stratification in this group of patients are still lacking. Although much effort has been spent on evaluating the long-term outcome after revascularization and medical treatments, the short-term course of these patients before revascularization is relatively unknown [1–3]. For the cardiologist, having decided on the diagnosis and the appropriate therapy it is of paramount importance to estimate the risk of critical events such as myocardial infarction and death before surgery. The existence of waiting lists offers a model in which the natural history and the short-term risk of patients with extensive coronary artery disease can be studied.
In this study we describe morbidity and mortality in patients waiting for coronary bypass surgery. We assessed determinants of these complications during the wait in order to improve identification of patients at risk at the time of selection for coronary artery bypass surgery.
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2. Methods |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionReferences |
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Patients accepted for coronary artery bypass graft (CABG) surgery were placed on one of three different waiting lists with the following priority categories: (a) imperative: surgery intended within 1 week; patients with left main and/or severe three-vessel disease with angina at rest and/or ST-T segment changes in the electrocardiogram (ECG) remained admitted at the coronary care unit or medium care unit awaiting their procedure; (b) urgent: surgery intended between 1 and 6 weeks; patients with left main or three-vessel disease with angina on exertion despite adequate anti-anginal medication but without complaints at rest and/or ST-T segment changes on the ECG; (c) routine: surgery intended within 3 months; all other patients. Patients who needed immediate surgery were not placed on a waiting list, but were sent to the operating room without delay.
The method of prioritization was described earlier in detail [4]. In summary, the key determinants were: extent of coronary artery disease, presence of left ventricular dysfunction, severity of anginal symptoms and response to medical therapy.
2.2. Study patients and follow-up
The study cohort consisted of the 360 consecutive patients included in a period of 7 months who were primarily presented and catheterized in the St. Antonius Hospital, Nieuwegein. Patients referred by other hospitals were not included. If accepted for CABG (or CABG with additional valve surgery) patients were placed on the waiting list with a priority of routine or urgent. These patients were followed from the moment of final acceptance for a revascularization procedure until the procedure took place, or until the procedure was cancelled or until the patient died. Patients who were scheduled for combined CABG and valve surgery were excluded if their valvular disease alone would have required surgical correction. Patients who needed immediate surgery were excluded from this study.
2.3. Data collection
Clinical variables gathered at the moment of acceptance were: severity of angina (New York Heart Association classification), extent and severity of coronary artery disease, cardiac history, period of unstable angina within 3 months prior to angiography, anti-anginal medication, exercise testing, cardiac enlargement on chest X-ray (cardiothoracic ratio >0.5) and angiographic left ventricular function.
A coronary artery was considered diseased if a 70% or more reduction in the luminal diameter was found. A left main coronary artery stenosis was considered significant if the diameter was reduced by 50% or more. Left ventricular function was classified in four categories: normal, slightly diminished, diminished, and poor. Furthermore, cardiovascular risk factors such as smoking, family history of coronary disease, diabetes mellitus, hypertension, hypercholesterolaemia, cerebrovascular arteriosclerosis and peripheral arteriosclerosis were recorded.
During the waiting time all cardiac events, admissions for a cardiac reason, priority shifts, change of CABG to percutaneous transluminal coronary angioplasty (PTCA), and cancellation of the procedure were registered.
2.4. Clinical events
Major adverse cardiac events (MACE) were defined as: (1) death; (2) myocardial infarction (fatal and non-fatal); and (3) an episode of unstable angina requiring immediate hospitalization. Multiple events were recorded. Myocardial infarction was diagnosed when at least two of the following were present: (1) a history of typical chest pain lasting for more than 30 min; (2) development of a new Q-wave; and (3) an increase in the serum creatinine kinase level to more than twice the normal value (>140 units/l) within 24 h after the start of complaints. Patients with symptoms of acute myocardial infarction who subsequently died were categorized as fatal myocardial infarction. Unstable angina was defined as angina at rest or aggravation of symptoms requiring hospitalization.
2.5. Statistics
All results were derived with SAS/PC programs (SAS Institute, Cary, NC). Continuous values are summarized as the mean±standard deviation. Categorical values are summarized as percentages. For the description of the waiting time the median and interquartile range were used. The relation between the time until first clinical events and baseline variables was univariately explored by means of Kaplan–Meier survival plots and formally statistically compared by the log-rank test. To examine the impact of covariates on events during waiting time, the proportional hazards model was used. Covariates were dichotomized in two categories: (a) an index group for which the risk was assumed to be increased was assigned a value of 1, as opposed to (b) the reference group that constituted all other cases, including the unclassified, and was attributed a value of 0. The ratio of the risk of the index group over the reference group is the hazard ratio (HR). First, a univariate HR was calculated by means of Cox regression for all baseline characteristics [5]. For clinically and statistically significant variables a risk ratio adjusted for covariates was calculated by means of a stepwise multivariate Cox proportional hazards model. For comparison of incidence densities exact P values were computed.
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3. Results |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionReferences |
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Overall, eight patients died (all of cardiac death) during the wait, seven patients suffered a myocardial infarction (four fatal, three non-fatal), and 33 episodes of unstable angina occurred requiring immediate hospitalization. The incidence density (per 100 patient years of waiting) of cardiac events during the whole waiting period was significantly higher in the urgent group in comparison with the routine group (97 and 22 per 100 patient years, respectively) (Table 2).
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4. Discussion |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionReferences |
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The majority of events took place during the first 30 days on the waiting list. We recorded an overall event rate of 13.4 deaths or myocardial infarctions per 100 patient years on the waiting list. The urgent group had the highest event rate (24.8). These findings were similar to the results of Silber et al. [7] who found that all deaths occurred within 4 weeks, the majority even within the first week. Naylor et al. [6] reported a crude overall event rate of 9.1 deaths or myocardial infarctions per 100 patient years. Silber et al. [7] found an incidence rate of 16.0 deaths per 100 patient years. This event rate exceeds by far the incidence rate of myocardial infarction in patients with stable angina not on a waiting list (2.4/100 patient years) as reported by Juul-Möller et al. [8]. Patients with a routine priority had to wait a median of 100 days, while patients on the urgent priority waiting list waited a median of 69 days. This contrasts distinctly with the experience from Ontario [6] with a median wait of 17 days and the findings of Silber et al. [7] with a mean wait of 31 days.
4.1. Triage
Our data show that triage was carried out according to the predefined key determinants [4]. In the multivariate analysis the extent of coronary artery disease (including the extent of left main stenosis), the presence of left ventricular dysfunction and the severity of anginal symptoms and response to medical therapy were not identified as independent risk factors for MACE. These findings indicate an appropriate use of the triage system. Therefore, the identification of a period of unstable angina as one of the independent predictors for complications was surprising because it is also one of the key determinants for deciding on priority. It indicates that a patient who has been stabilized after a period of unstable angina will remain susceptible for another period of unstable angina or even myocardial infarction in the near future. Triage might be improved if more weight is given to a period of unstable angina just prior to acceptance. We emphasize that this should be distinguished from acute unstable angina at admission during the waiting period. Surgery carried out within hours or a few days after onset could even increase mortality. Those patients were assigned the priority imperative and were excluded from our study.
The risk factors smoking and familial cardiovascular disease interact with the final decision on the waiting list. Taking the interaction into account by means of a multivariate analysis, the resulting ascending order of risk of a cardiac event during the waiting time was: non-smoker on the routine waiting list, smoker on the routine list, smoker on the urgent list and the highest risk for the non-smoker on the urgent list. The same pattern was seen for the risk factor familial cardiovascular disease. Thus, patients in the urgent group, despite lacking one of the mentioned risk factors, were at the greatest risk for complications. Apparently, patients with these known risk factors are more easily placed in the urgent group, while in view of their clinical status this is in some cases not necessary. On the other hand patients without these known risk factors are placed in the urgent group because of their clinical features. We hypothesized that these latter patients probably had a more advanced or severe stage of the disease than smokers or patients with familial cardiovascular disease who were placed on the urgent list. The above indicates that the importance of these known risk factors is probably overrated.
4.2. Implications
In our study, 93% of the group with low priority did not experience any adverse cardiac event. It follows from the Kaplan–Meier curve that if a maximum cumulative event rate of 7% was also to be targeted for the urgent group, the consequence would be to operate on all urgent patients within 14 days.
In conclusion, our findings have two implications. Firstly, on a patient level a more appropriate selection is needed in order to give even higher priority to patients at the greatest risk for ischaemia-related adverse events. However, as a consequence a considerable number of patients will be granted a lower priority on the waiting list and will have a longer waiting time. The consequence of this approach can not be foreseen. Secondly, as long as complications in coronary heart disease can not be predicted more accurately – because of the pathophysiological mechanism of unstable angina and myocardial infarction, i.e. interplay of plaque rupture, increased thrombocyte aggregation and coronary spasm – and considering the fact that complications occur relatively early during the wait, at this moment the only way to diminish the complication rate is to radically reduce waiting times. Patients should be offered the option of surgery within 1 or 2 weeks of catheterization, requiring a major expansion in surgical capacity even at the cost of a certain loss of efficiency [9].
In summary, we showed that most complications on the waiting list for CABG occur in the first 30 day period. Patients who have experienced unstable angina in a period <3 months before being placed on the waiting list remain at increased risk of major adverse cardiac events. In the absence of more adequate predictors of these events the only way to diminish the complication rate is a drastic reduction in waiting times.
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Acknowledgments |
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References |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionReferences |
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H. Rexius Should patients with stenosis of the left main coronary artery waiting for bypass grafting be given priority? Can. Med. Assoc. J., August 16, 2005; 173(4): 381 - 382. [Full Text] [PDF]
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