Abstract

Objective: Clinical trials and practice guidelines have established the efficacy of early invasive strategy for high risk acute coronary syndrome (ACS) patients. This analysis was undertaken to detect the predictors of in-hospital cardiac catheterization (prior to hospital discharge) in patients with ACS in Kuwait and to assess if this use of early catheterization was according to published guidelines.

Methods: We analyzed data from a prospective registry of 2054 consecutive patients admitted to all 7 general hospitals in Kuwait with the diagnosis of ACS over a period of 6 months in 2004.
Results: Citizens were more likely to receive in-hospital catheterization than expatriates (52.1% vs 38.6%; odds ratio 1.7; 95% confidence interval [CI], 1.4 to 2.2; p < 0.001). Patients with recurrent ischemia were more likely to undergo in-hospital catheterization than patients without recurrent ischemia (55.9% vs 12.2%; odds ratio 11.2; 95% CI, 8.6 to 14.5; p < 0.001). Two coronary artery disease risk factors (hyperlipidemia and positive family history) were associated with high rate of in-hospital cardiac catheterization (respectively, odds ratio 1.3; 95% CI, 1.2 to 2; p < 0.001 and odds ratio 1.5; 95% CI, 1.3 to 2.3; p < 0.001).

Conclusion: Although high risk patients benefit the most from an early invasive strategy after ACS, this strategy was persevered for those with recurrent ischemia and citizens. Other risk factors were not determinants for in-hospital cardiac catheterization. Thus, there is substantial opportunity to improve the use of this effective therapy in high risk patients. Heart Views 2009;10(3)104-109. © Gulf Heart Association 2009.

Keywords: ¨ acute coronary syndrome ¨ cardiac catheterization ¨ Kuwait



Introduction

Acute coronary syndromes (ACS) are a leading cause of mortality and morbidity1,2. Part of the management of ACS involves deciding which patient receives conservative therapy and which one receives early invasive treatment. European and American guidelines advocate early cardiac catheterization for moderate or high risk patients but not for low risk patients3-5. Yet some registries show that early invasive management is less frequently practiced in ACS patients with high risk features6. Several ACS trials and registries have demonstrated that, often, the increased use of invasive therapy is related solely to whether or not a cardiac catheterization laboratory is available onsite. Those hospitals that have catheterization laboratory tend to carry out more early invasive therapy than those who do not7,8.

In Kuwait, we have a unique setting where none of the hospitals that admit and care for ACS patients have an onsite cardiac catheterization laboratory. All ACS patients are admitted to seven general hospitals where they receive appropriate medical therapy and are then stratified into groups that get transferred, for cardiac catheterization, to the only cardiac centre in the country or continue to receive medical therapy until hospital discharge. There are no data about our catheterization pattern and adherence to clinical guidelines as relates to the use of in-hospital cardiac catheterization (catheterization prior to hospital discharge) in ACS patients in Kuwait. We carried out this study to identify determinants of in-hospital cardiac catheterization in ACS patients and to see whether our use of early catheterization followed published guidelines.


Methods


Data were analyzed from the Kuwait Acute Coronary Syndromes (KACS) Registry1. The 7 general hospitals in Kuwait that admit patients with ACS participated in this registry. These hospitals were Mubarak Al-Kabeer, Al-Amiri, Al-Adan, Al-Farwania, Al-Jahra, Al-Sabah and Kuwait Oil Company. At each hospital, designated physicians prospectively identified consecutive patients admitted with ACS over a period of six months, from December 2003 through May 2004. Several variables were collected, including patients’ demographics, past medical history, diagnosis on admission, vital signs at presentation, diagnostic electrocardiogram (ECG), peak creatine kinase enzyme and creatine kinase MB isoenzyme, peak cardiac troponin I, blood sugar, fasting serum lipids, diagnosis at discharge, in-hospital transfer for cardiac catheterization, discharge medications, and in-hospital outcomes including recurrent angina, reinfarction, heart failure, cardiac shock and in-hospital mortality. Hypertension was defined by one of the following criteria: History of hypertension diagnosed and treated with medication, diet or exercise; blood pressure greater than 140mm Hg systolic or 90mm Hg diastolic on at least two occasions; current use of antihypertensive therapy. Hyperlipidemia was defined as having a history of elevated cholesterol and triglycerides diagnosed and/or treated by a physician. Data forms were checked for completeness at a national coordinating center and were returned for correction to the participating hospitals when necessary.

Patient care at each participating hospital was performed according to usual practice, independent of the KACS registry. The diagnosis of different types of ACS was based on the American College of Cardiology key data elements and definitions for measuring the clinical managements and outcomes of patients with acute coronary syndromes9. Cardiac biomarkers were measured locally at each hospital’s laboratory, using its own assays and reference range. For the diagnosis of unstable angina (UA) to be made, the following criteria were necessary. First, clinical presentation: angina that occurred at rest and was prolonged, usually lasting more than 20 minutes; new-onset angina of at least Canadian Cardiovascular Society (CCS) class III severity or recent acceleration of angina reflected by an increase in severity of at least one CCS class to at least CCS class III. Second, the biochemical cardiac markers had to be within the normal range or slightly elevated, but not reaching the range at which myocardial infarction (MI) occurs. Third, the ECG at presentation had to have ST segment depression or T wave inversion; if there were no ECG changes at presentation, then one of the following was required: A history of MI, positive exercise stress test or previous angiogram showing significant coronary artery disease. For the purpose of this analysis, we also stratified patients by risk group. Patients with diabetes, ST-segment depression on presenting ECG and raised cardiac enzymes were designated as high risk non-ST-segment elevation myocardial infarction (NSTEMI) group. Patients who suffered large ST-segment elevation myocardial infarction (STEMI) with ECG indicating anterior, anteroseptal or anterolateral locations were designated as high risk STEMI group.


Statistical analysis


The two-tailed t-test was used to analyze for differences in continuous variables (age). The association between various patient factors and the presence or absence of in-hospital cardiac catheterization was studied by univariate logistic regression analysis. These patient factors included ethnicity, risk factors for coronary artery disease (age, gender, diabetes, hypertension, hypercholesterolemia, smoking, family history and previous AMI) and clinical factors (ST-segment elevation on presentation, congestive heart failure and recurrent ischemia). Patient factors univariately associated with outcome (P < 0.10) were included in a multivariate forward stepwise logistic regression model. The prognostic accuracy of the model was estimated (goodness-of-fit) using Hosmer-Lemeshow statistics. All analyses were performed with the SPSS statistical package version13.


Results


Overall, 2054 patients with confirmed ACS were identified during KACS registry. In-hospital catheterization (catheterization prior to hospital discharge) was performed in 368 patients (18%). Table 1 summarizes the baseline characteristics of patients according to in-hospital catheterization. The mean age of patients who underwent in-hospital catheterization was 56±11.4 compared to 55.4±12.2 years for patients who were treated conservatively (p = 0.24). Of the variables studied, patients known to have hyperlipidemia or family history of ischemic heart disease were significantly more likely to receive in-hospital catheterization as opposed to those receiving conservative therapy (for hyperlipidemia, odds ratio 1.57; 95% CI, 1.2 to 2; for family history, odds ratio 1.74; 95% CI, 1.3 to 2.3). There were no statistical differences in the rate of in-hospital catheterization for ACS patients according to a past history of angina, myocardial infarction, percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) (odds ratios 1.27, 1.0, 1.13 and 1.0, respectively).

Table 2 shows the use of in-hospital cardiac catheterization by presence or absence of high risk features. The features univariately associated with in-hospital catheterization were high risk NSTEMI and recurrent ischemia (odds ratio 1.5; 95% CI, 1.2 to 1.9 and odds ratio 11.2; 95% CI, 8.6 to 14.5, respectively). Several other high risk features were not associated with increased use of cardiac catheterization, and these included high risk STEMI, the presence of heart failure at presentation or during hospitalization, the presence of ST-segment elevation or depression on presenting electrocardiogram and the presence of elevated troponin levels.

Finally, a multivariate logistic regression model was used to identify features in the overall cohort that were independently associated with the decision to undergo in-hospital cardiac catheterization (Table 3). Citizenship, recurrent ischemia, hyperlipidemia and family history of ischemic heart disease were found to be independently associated with in-hospital catheterization (odds ratios 1.8, 11.8, 1.3 and 1.5 respectively). After recurrent ischemia, citizenship was the most important independent predictor of in-hospital catheterization, with citizens being twice as likely as expatriates to undergo the procedure (odds ratio 1.8; 95% CI, 1.3 to 2.3).

 

Table 1: Baseline characteristics of study cohort

MI = myocardial infarction, PCI = percutaneous coronary intervention, CABG = coronary artery bypass graft, DM2 = type 2 diabetes mellitus, HTN = hypertension.

 

Table 2: High risk features and association with in-hospital cardiac catheterization

See methods for definition of “High risk”. NSTEMI = non-ST-segment elevation myocardial infarction, STEMI = ST-segment elevation myocardial infarction, LVF = left ventricular failure. CHF = congestive heart failure.

Discussion


Our study has revealed two important findings relating to the use of cardiac catheterization prior to hospital discharge for ACS patients in Kuwait. First, high-risk ACS patients were not more likely to undergo catheterization when compared to lower risk patients. Second, the two most important determinants of in-hospital catheterization were recurrent ischemia and Kuwaiti citizenship. These findings are not consistent with guidelines and recommendations. Randomized trials comparing early intervention versus conservative strategies in ACS advocate revascularization for moderate or high risk patients but not for low risk patients4,10. These sources suggest that high risk ACS patients have the most to gain from early revascularization11,12. According to the updated ACC/AHA guidelines, high risk patients are those presenting with ischemic electrographic changes, elevated troponin levels, new heart failure symptoms, left ventricular dysfunction, prior PCI within 6 months, prior CABG and hemodynamic instability13. In our study, patients who had left ventricular failure at presentation had the same likelihood of undergoing catheterization as those without this complication. There was no difference in the rate of catheterization for patients with previous revascularization (PCI or CABG) compared to those without. The same was true for patients with new electrographic changes and new heart failure. Though disappointing, similar findings have been reported in the literature. The CRUSADE investigators found that high risk ACS patients (represented by prior CABG, prior or current heart failure and those presenting with faster heart rate) underwent less invasive management compared to lower risk patients14. A possible explanation for this odd finding is that features that impart a high risk onto an ACS patient, are those same features that make a treating physician shy away from an invasive management due to the high risk involved. The overall net result is carrying out more catheterization in lower risk patients.

In our study, a main determinant of in-hospital cardiac catheterization was citizenship. The disparity of the early invasive strategy between citizen and expatriate patients demonstrated in this analysis appears to be related to treatment bias. The source of this bias is probably the fact that cardiac catheterization service is not free for expatriates living in Kuwait and many of them cannot afford it. Add to that the fact that some of the expatriates prefer to postpone the invasive procedure and have it done in their home countries. This treatment bias presents a significant obstacle that must be overcome to improve the outcomes for expatriates with ACS who are unlikely to be managed aggressively in current practice.

While other studies have found younger age to be an important predictor of early cardiac catheterization, that was not the case in our study. Results from the CRUSADE analysis6 showed that younger healthier patients selectively undergo early invasive management in the United States, while older patients with co-morbidities are treated conservatively. A possible explanation for the absence of age influence in our study is the relatively young age of our population, with a mean age of 56.2 ± 11.4 for the in-hospital catheterization group and 55.4 ± 12.2 for the conservative therapy group.

In summary, our study shows that the use of in-hospital cardiac catheterization in patients with ACS in Kuwait is not entirely based on the strength of the indication for the procedure. Citizenship played a major role in determining who underwent the procedure. While recurrent ischemia after admission, hyperlipidemia and family history of IHD played a role, no other factor studied influenced the use of catheterization early after ACS. Therefore, the need for promoting the use of risk stratification, and developing unified criteria across Kuwait hospitals for selecting candidates for an early invasive strategy is very much needed.

 

 

Table 3: Forward stepwise multivariate logistic regression using variables with a univariate p value < 0.1 from tables 1 & 2.

Limitations


The main limitation of this registry is the lack of long term outcome data. Another limitation is the lack of specific information as to why some high risk patients did not undergo cardiac catheterization.¨
 

References:


1. Zubaid M, Rashed W, Saad H, et al. Kuwait Acute Coronary Syndromes Registry; Base Line Characteristics, Management Practices and In-Hospital Outcomes of Patients Hospitalized with Acute Coronary Syndromes in Kuwait. Med Princ Prac 2007; 16: 407- 412.

2. American Heart Association. Heart disease and Stroke Statistics – 2004 Update. Dallas, TX: American Heart Association, 2003.

3. Fragmin and Fast Revascularization during Instability in Coronary artery disease (FRISC II) Investigators; Invasive compared with non-invasive treatment in unstable coronary-artery disease: FRISC II prospective randomized multicentre study. Lancet. 1999; 354: 708-715.

4. Cannon CP, Weintraub WS, Domopoulos LA, et al; Comparison of early invasive and conservative strategies in patients with unstable angina and non-ST elevation myocardial infarction treated with the glycoprotein IIb/IIIa inhibitor triofiban. N Engl J Med. 2001; 344: 1879-1887.

5. Fox KA, Poole-Wilson PA, Henderson RA, et al; Randomized Intervention Trial of Unstable Angina Investigators. Interventional versus conservative treatment for patients with unstable angina or non- ST elevation myocardial infarction: British Heart Foundation RITA 3 randomized trial: Randomized Intervention Trial of Unstable Angina. Lancet 2002; 360: 743- 751.

6. Bhatt DL, Roe MT, Peterson ED, et al; Utilization of Early Invasive Management Strategies for High Risk Patients with Non-ST Elevation Acute Coronary Syndromes: Results from CRUSADE Quality Improvement Initiative. JAMA 2004; 291: 2096-3104.

7. Roe MI, Chen AY, Delong ER, et al; Patterns of transfer for patients with non-ST segment elevation acute coronary syndrome from community to tertiary care hospitals. Am Heart J. 2008 Jul; 153 (1): 185 - 192.

8. Dobrycki S, Meznski G, Kralisg P; Is transport with platelet GP IIb/IIIa inhibitor for primary percutaneous coronary intervention more efficient than on site thrombolysis in pathients with STEMI admitted to community hospitals ?: Kardiol Pol. 2006 Aug; 64 (8): 793 -799.

9. Cannon CP, Battler A, Brindis RG, et al; American College of Cardiology key data elements and definitions for measuring the clinical managements and outcomes of patients with acute coronary syndromes: a report of the American College of Cardiology Task Force on Clinical Data Standards ( Acute Coronary Syndromes Writing Committee). J Am Coll Cardiol 2001; 2114-2130.

10. Jollis JG, Delong ER, Peterson ED, et al; Outcome of acute myocardial infarction according to the specialty of the admitting physician. N Eng J Med. 1996; 335: 1880-1887.

11. Diderholm E, Anderson B, Frostfiedt G, et al; Fast Revascularization during Instability in Coronary artery disease (FRISC ??) Investigators. The prognostic and therapeutic implication s of increased troponin T levels and ST depression in unstable coronary artery disease: the FRISC II invasive troponin T electrocardiogram substudy. Am Heart J.2002; 143: 760-767.

12. Diderholm E, Anderson B, Frostfiedt G, et al; ST depression in ECG at entry indicates severe coronary artery lesions and large benefits of an early invasive treatment strategy in unstable coronary artery disease: FRISC II ECG substudy: the Fast Revascularization during Instability in Coronary artery disease. Eur Heart J. 2002; 23: 41-49.

13. Braunald ME, Antman EM, Beasley JW, et al; ACC/ AHA 2002 guidelines update for the management of patients with unstable angina and non- ST- segment elevation myocardial infarction- summery article: a report of the American College of Cardiology L American Heart Association task force on practice Guidelines. J Am Coll Cardiol 2002; 40: 1366-1374.

14. Yan AT, Tan M, Fitchett D, et al; Canadian Acute Coronary Syndromes Registry Investigators. One – year outcome of patients after acute coronary artery syndromes. Am J Cardiol 2004; 94: 25-29.


 

The Coronary Arteriogram and Mason Sones, Jr., M.D.   "We've killed him!" exclaimed Dr. Mason Sones in horror as he watched the inadvertent injection of dye into the right coronary artery of his patient1. The event happened during an aortic root injection in a 26-year-old patient with rheumatic heart disease, when the catheter whiplashed into the ostium of the right coronary artery. That was in 1958 and conventional wisdom of the day was that non-oxygenated contrast medium in the coronary arteries would cause fatal ventricular fibrillation. This did not happen, and Sones concluded that selective doses of smaller, more diluted amounts of contrast agent introduced directly into individual coronary arteries would finally make consistently clear arteriography of selected coronary arteries possible. Although the performance of this selective coronary arteriogram was unintentional, it was the first direct injection of a contrast agent into a coronary artery. Other researchers improved the technique and catheter design and Sones' coronary arteriography became widely used. Sones was also the first to combine cardiac catheterization, angiography, and high speed X-ray motion picture photography as a single procedure (cinecoronary arteriography) and thus making it possible to visualize, record and analyze the rapid circulatory movements in the heart and coronary arteries2. Sones' technique – cinecoronary arteriography – is the foundation stone of our current knowledge of coronary artery disease and its present treatment. It revolutionized the practice of 20th century cardiology. Dr. Mason Sones received his M.D. from the University of Maryland School of Medicine in 1943 and in 1950, he joined the Cleveland Clinic Foundation as the Director of Pediatric Cardiology and the Cardiac Laboratory and later as Director of the Clinic's Department of Cardiovascular Disease. He was honored with numerous awards during his career. He died of lung cancer at the age of 662. The pioneer cardiovascular surgeon Dr. Rene G. Favaloro said: "Without the work of Dr. Mason Sones, Jr. – the most important contributor to modern cardiology – all our efforts in myocardial revascularization would have been fruitless2." The coronary arteriogram continues to reign as the imaging modality for the diagnosis and management of coronary artery disease in the 21st century.                                                                       Rachel Hajar, M.D. References: 1. Ryan TJ. The coronary angiogram and its seminal contribution to cardiovascular medicine over five decades. Circulation. 2002;106:752-756. 2. Hall RJ. In memoriam: F. Mason Sones, Jr., M.D. Texas Heart Institute Journal. 1985;12(4):357-358.