Efficacy of exercise thallium-201 scintigraphy in the diagnosis and prognosis of coronary artery disease. American College of Physicians

Deferring angioplasty in intermediate coronary lesions based on coronary flow criteria is safe: comparison of a deferred group to an intervention group

The decision for revascularization in patients with intermediate coronary lesions remains a challenging topic, particularly when objective data of reversible ischemia are lacking. In some of the patients, coronary revascularization is performed or deferred without definitive evidence on the clinical significance of the coronary stenosis. We investigated the usefulness of coronary flow reserve (CFR) measurements in 28 patients with intermediate coronary lesions. We compared 20 patients who underwent angioplasty based on Doppler-wire-derived CFR with 8 patients for whom angioplasty was deferred (diameter stenosis of 50.7 +/- 2.0% versus 46.5 +/- 3.1%, P < 0.0001 and CFR of 1.80 +/- 0.32 versus 2.65 +/- 0.11, P = 0.002, respectively). Angioplasty resulted in normalization of the CFR to 2.57 +/- 0.53 (P < 0.0001, versus the baseline value). During a follow-up period of 58.1 weeks (range 23-149 weeks), eight patients in the revascularization group were readmitted to the hospital, one of them with a myocardial infarction in the territory of the target vessel, compared with only one admission in the deferred group. Target-vessel revascularization was performed in three patients (a fourth patient declined it) in the former group, compared with only one in the latter. Symptomatic improvement or no change in clinical status was observed in the majority of patients in both groups (90% in the revascularization group and 87.5% in the deferred group). We conclude that in a selected group of patients with intermediate coronary lesions, measurement of CFR may be a useful tool in determining the need for revascularization based on its physiologic significance. Importantly, deferring PTCA in patients with intermediate lesions and normal CFR values seems to be safe.

Preparing the azotemic diabetic patient for surgery

Azotemic diabetic patients have more risk of complications during or after surgery than those without diabetes and azotemia. These complications include infection, excessive bleeding, cardiovascular events, and electrolyte imbalance. The appropriate preoperative evaluation, measures to be taken to avoid the complications, and how to adequately manage blood sugar during surgery is discussed.

Mechanisms of limited maximum coronary flow in severe single-vessel coronary artery disease in humans due to vertical steal

We evaluated the usefulness of a decrease in the average peak velocity from 4 to 10 minutes after infusion of dipyridamole for detecting myocardial ischemia in 50 patients, including patients with a prior myocardial infarction. The decrease in the average peak velocity from 4 to 10 minutes associated with vertical steal and combined with a coronary flow reserve of < 1.6 had a high predictive value for myocardial ischemia in patients with or without prior myocardial infarction.

Incremental value of simultaneous assessment of myocardial function and perfusion with technetium-99m sestamibi for prediction of extent of coronary artery disease

OBJECTIVES

This study assessed the incremental value of technetium-99m myocardial single-photon emission computed tomography (SPECT) and simultaneous first-pass radionuclide angiography, when added to treadmill exercise, for prediction of the extent of coronary artery disease.

BACKGROUND

Technetium-99m count statistics permit the simultaneous assessment of myocardial perfusion and function. However, whether this characteristic improves prediction of the extent of coronary artery disease remains unknown.

METHODS

We studied 70 consecutive patients who had coronary angiography within 6 months of the scintigraphic study. All patients underwent a symptom-limited treadmill exercise test. Treadmill data were summarized using a previously validated score. Left ventricular ejection fraction and regional wall motion were evaluated from a first-pass radionuclide angiogram acquired at peak treadmill exercise in the anterior view. Perfusion was assessed visually. Extent of angiographic disease was expressed as the presence or absence of multivessel disease (more than two coronary artery territories with > 50% stenosis) and as a score that reflects the location of severe (> 75%) stenosis.

RESULTS

Stepwise addition of scintigraphic data (perfusion first, followed by function) to the treadmill score showed significant incremental value for prediction of the angiographic score at each step; exercise ejection fraction alone was the strongest independent predictor. Discriminant accuracy for detection of multivessel disease was also improved by the addition of perfusion information to the treadmill score and addition of regional wall motion analysis to both of them. In this case, ejection fraction failed to show independent value.

CONCLUSIONS

The addition of simultaneously performed sestamibi perfusion SPECT and first-pass radionuclide angiography to the treadmill exercise test significantly improved prediction of the extent of coronary artery disease.

Trade-offs in producing patient-specific recommendations from a computer-based clinical guideline: a case study

This case study explored 1) how much online clinical data is required to obtain patient-specific recommendations from a computer-based clinical practice guideline, 2) whether the availability of increasing amounts of online clinical data might allow a higher specificity of those recommendations, and 3) whether that increased specificity is necessarily desirable. The "quick reference guide" version of the guideline for acute postoperative pain management in adults, developed by the Agency for Health Care Policy and Research, was analyzed. Patient-specific data items that might be used to tailor the computer's output for a particular case were grouped into rough categories depending on how likely they were to be available online and how readily they might be determined from online clinical data. The patient-specific recommendations were analyzed to determine to what degree the amount of text produced depended on the online availability of different categories of data. An examination of example recommendations, however, illustrated that high specificity may not always be desirable. The study provides a concrete illustration of how the richness of online clinical data can affect patient-specific recommendations, and describes a number of related design trade-offs in converting a clinical guideline into an interactive, computer-based form.

Clinical outcome of deferring angioplasty in patients with normal translesional pressure-flow velocity measurements

OBJECTIVES

The objective of this study was to determine the feasibility, safety and outcome of deferring angioplasty in patients with angiographically intermediate lesions that are found not to limit flow, as determined by direct translesional hemodynamic assessment.

BACKGROUND

The clinical importance of some coronary stenoses of intermediate angiographic severity frequently requires noninvasive stress testing. Direct translesional pressure and flow measurements may assist in clinical decision making in patients with such stenoses.

METHODS

Translesional spectral flow velocity (Doppler guide wire) and pressure data were obtained in 88 patients for 100 lesions (26 single-vessel and 74 multivessel coronary artery lesions) with quantitative angiographic coronary narrowings (mean +/- SD diameter narrowing 54 +/- 7% [range 40% to 74%]). Target lesion angioplasty was prospectively deferred on the basis of predetermined normal values, defined as a proximal/distal velocity ratio < 1.7 or a pressure gradient < 25 mm Hg, or both. Patients were followed up for 9 +/- 5 months (range 6 to 30).

RESULTS

In the deferred angioplasty group, translesional velocity ratios were similar to those of a normal reference group (mean 1.1 +/- 0.32 vs. 1.3 +/- 0.55) and significantly lower than those of a reference cohort of patients who had undergone angioplasty (2.27 +/- 1.2, p < 0.05). The mean translesional pressure gradient in the deferred angioplasty group was also lower than that in the angioplasty group (10 +/- 9 vs. 45 +/- 22 mm Hg, p < 0.001). At follow-up in the deferred angioplasty group, four, six, zero and two patients, respectively, had had subsequent angioplasty, coronary artery bypass graft surgery or myocardial infarction or had died. In one patient, death was related to angioplasty of a nontarget artery lesion, and one patient with multivessel disease had a cardiac arrest due to ventricular fibrillation 12 months after lesion assessment. Among the 10 patients requiring later angioplasty or coronary artery bypass grafting, only six procedures were performed on target arteries. No patient had a complication of translesional flow or pressure measurements.

CONCLUSIONS

These data demonstrate the safety, feasibility and clinical outcome of deferring angioplasty of coronary artery narrowings associated with normal translesional coronary hemodynamic variables. Given the practice of performing angioplasty without ischemic testing or when testing is inconclusive, translesional hemodynamic data obtained at diagnostic catheterization can identify patients in whom it is safe to postpone angioplasty.

Improving clinical guidelines with logic and decision-table techniques: application to hepatitis immunization recommendations

Clinical practice guidelines can be clarified, verified, and simplified by the use of logical analysis and the application of decision-table techniques. This methodology is applied to a CDC guideline for the prevention of perinatal transmission of hepatitis B by immunization. Relevant clinical variables are identified and possible values for each variable are defined. An exhaustive enumeration of value combinations is generated. Logically impossible combinations are identified and eliminated. The guideline's recommendations are next translated into a set of rules and compared with the remaining value combinations. Variable combinations that are not covered by guideline recommendations represent incomplete guideline specifications. Inconsistency can be identified by finding identical condition sets in two or more rules. The procedure demonstrates that the hepatitis guideline is incomplete. Logical analysis can improve the quality of clinical practice guidelines by assuring comprehensiveness and consistency.

Translesional pressure-flow velocity assessment in patients: Part I

Interventional physiology presents the operator with objective data to facilitate decision making. A thorough and validated understanding of the alterations of pressure and flow in the human coronary circulation is currently in progress. As illustrated in the case studies, some situations have data which may initially appear contradictory or unhelpful to clinical practice. These data should provide a framework to understand the dynamic physiology producing the clinical syndromes in patients undergoing coronary interventional procedures. Future Interventional Physiology Rounds will examine coronary pressure-flow responses during directional atherectomy, stents, and acute myocardial infarction.

Screening diabetic transplant candidates for coronary artery disease: identification of a low risk subgroup

Coronary artery disease is the major cause of death in diabetic renal transplant recipients. Because one-third of diabetic transplant candidates have clinically silent coronary artery disease, many transplant centers recommend coronary angiography prior to transplantation. However, angiography is expensive and may precipitate acute renal failure. Therefore, we developed a noninvasive screening algorithm to identify patients at low risk for coronary artery disease (CAD), defined as one or more coronary stenoses > or = 50% diameter. We performed coronary angiography in 141 consecutive asymptomatic Caucasian type I diabetic renal transplant candidates. Fourteen of 16 patients age 45 or older had CAD. One hundred and twenty-five patients under age 45 were randomly divided into two groups. Ninety patients were used to identify clinical factors significantly associated with CAD which included smoking for five or more pack years, nonspecific ST-T wave changes on electrocardiogram, and diabetes duration 25 years or longer. The screening algorithm, "CAD is predicted in diabetic transplant candidates under age 45 with any of the above risk factors," was then tested in the remaining 35 patients and in 35 additional patients. In these 70 patients, the algorithm had a sensitivity of 97% and a negative predictive accuracy of 96%. We conclude that coronary angiography should be recommended to Caucasian type I diabetic renal transplant candidates age 45 or older because of the high probability of disease. In patients younger than 45 without a smoking history, ST-T wave changes on EKG, or diabetes longer than 25 years, the likelihood of CAD is low and angiography can be avoided.

Assessing the hemodynamic significance of coronary artery stenoses: analysis of translesional pressure-flow velocity relations in patients

OBJECTIVES

The purpose of this study was to examine the relation among the angiographic severity of coronary artery lesions, coronary flow velocity and translesional pressure gradients.

BACKGROUND

Determination of the clinical and hemodynamic significance of coronary artery stenoses is often difficult and inexact. Angiography has been shown to be an imperfect tool for determining the physiologic significance of eccentric or irregular coronary lumen narrowing.

METHODS

Using a 0.018-in. (0.046 cm) intracoronary Doppler-tipped angioplasty guide wire, spectral flow velocity data both proximal and distal to coronary stenoses were compared with translesional pressure gradient measurements and angiographic data obtained during cardiac catheterization in 101 patients. There were 17 patients with normal angiographic findings and 84 with coronary artery disease, with lesions ranging from 28% to 99% diameter narrowing. Patients with coronary disease were assigned to two groups on the basis of translesional gradients at rest. Group A (n = 56) had gradients < 20 mm Hg, and Group B (n = 28) had gradients > or = 20 mm Hg.

RESULTS

Proximal average peak velocity, diastolic velocity integral and total velocity integral were slightly but statistically lower in Group A; however, the distal average peak velocity and diastolic and total velocity integrals were all markedly (all p < 0.01) decreased in patients with gradients > or = 20 mm Hg (Group B). In addition, the ratio of proximal to distal total flow velocity integral was higher in Group B (2.4 +/- 1.0) than in group A (1.1 +/- 0.3, p < 0.001). There was a strong correlation between translesional pressure gradients and the ratios of the proximal to distal total flow velocity integrals (r = 0.8, p < 0.001), with a weaker relation between quantitative angiography and pressure gradients (r = 0.6, p < 0.001). In angiographically intermediate stenoses (range 50% to 70%), angiography was a poor predictor of translesional gradients (r = 0.2, p = NS), whereas the flow velocity ratios continued to have a strong correlation (r = 0.8, p < 0.001). Only two patients with a proximal/distal total flow velocity ratio < 1.7 had a translesional gradient > 30 mm Hg. Both patients had a very proximal lesion in a nonbranching right coronary artery.

CONCLUSIONS

These data demonstrate that in branching human coronary arteries, a close relation exists between translesional hemodynamics and distal coronary flow velocity. Translesional coronary flow velocity is a new and easily applicable method for determining the hemodynamic significance of coronary artery stenoses that is superior to angiography and can be applied at the time of diagnostic catheterization. These data will provide a rational approach to making decisions on the use of coronary interventional techniques when angiographic findings are questionable.

Assessment of angiographically intermediate coronary artery stenosis using the Doppler flowire

Determination of the clinical and hemodynamic significance of coronary stenoses is often difficult and inexact. Angiography and coronary vasodilator reserve have been shown to be imperfect tools to determine the physiologic significance of coronary stenoses. Spectral flow velocity data, both proximal and distal to coronary stenoses, using an 0.018-in intracoronary Doppler-tipped angioplasty guidewire, were compared to translesional pressure gradients and angiography during cardiac catheterization. Patients were divided into 2 groups based on resting translesional gradients: Group 1 had gradients < 20 mm Hg and group 2 had gradients > or = 20 mm Hg. Proximal average peak velocity, diastolic velocity integral, and total velocity integral were statistically significantly lower in Group 1. The distal average peak velocity, and diastolic and total velocity integrals were all significantly (p < 0.01) decreased in patients with gradients > 20 mm Hg (group 2). The ratio of proximal-to-distal total flow velocity integral was also higher in group 2 patients (2.3 +/- 0.9) compared with group 1 (1.1 +/- 0.2; p < 0.001). There was a strong correlation between translesional pressure gradients and the ratios of the proximal-to-distal total flow velocity integrals (r = 0.8, p < 0.001) with a weaker relationship between quantitative angiography and pressure gradients (r = 0.6, p < 0.001). Angiography was a poor predictor of translesional gradients in angiographically intermediate stenoses (range 50-70%; r = 0.2, p = NS), while the flow velocity ratios continued to have a strong correlation (r = 0.8, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

A survey of exercise testing practice in Scottish hospitals

A 1989 survey (unpublished) of exercise testing practice in Scotland suggested that there were important differences in the practice of exercise testing between hospitals. A postal questionnaire was sent to 30 teaching and district general hospitals in 1991 and followed up by telephone questioning of consultants. The numbers of exercise tests performed had increased to 22,012 in 1990, and a greater proportion were performed in district general hospitals. General practitioners had very limited access to the service but hospital doctors of any grade had almost free access. Rationing of early post myocardial infarction testing led to attempts to define "high risk" post infarction patients and this included inappropriate patients in many hospitals. A variety of different protocols was used. Eighteen out of 30 hospitals surveyed discontinued beta blockers but only four hospitals took account of antianginal, antihypertensive or other medication, and all but one exercised patients while on digoxin. In the majority of hospitals decisions regarding drug therapy were taken by individual physicians. A variety of personnel reported tests, many without specialist training in cardiology. Even among consultants there was no concerns on the degree of ST depression which was significant. Exercise tests performed in different hospitals in Scotland are not comparable due to the wide variation in patient selection, test conditions, and interpretation of tests. This problem is likely to be exacerbated by the multiple personnel involved in all aspects of testing. It seems probable that there is a problem throughout the United Kingdom, and that there is a need for guidelines.

Prognostic value of exercise thallium scintigraphy in patients with good exercise tolerance and a normal or abnormal exercise electrocardiogram and suspected or confirmed coronary artery disease

Exercise thallium scintigraphy is widely used to assess prognosis in patients with suspected or proven coronary artery disease. The incremental prognostic value of this technique in patients who have good exercise tolerance has not been well studied. Two hundred ninety-nine patients with known or suspected coronary artery disease without prior myocardial infarction or revascularization procedure referred for exercise myocardial perfusion imaging and able to exercise to greater than or equal to stage III of the Bruce protocol were included. After a mean follow-up of 50 +/- 10 months, there were 15 cardiac events (5%). The incidence of cardiac events was 10 versus 3% (p less than 0.001) in patients with an abnormal versus normal thallium-201 scan, and 9 versus 3% (p = 0.03) for an abnormal versus normal exercise electrocardiogram. When the 185 patients with a normal exercise electrocardiogram were examined, the incidence of cardiac events was 3% (5 of 150) in patients with a normal scan versus 0% (0 of 35) in patients with an abnormal scan. In the 114 patients with an abnormal exercise electrocardiogram, an abnormal thallium-201 scan was predictive of cardiac events (18% [8 of 44] versus 3% [2 of 70]; p = 0.006). Stepwise logistic regression analysis selected an abnormal thallium-201 scan and abnormal exercise electrocardiogram, low peak exercise heart rate, and male gender as independent variables associated with a significant increased risk of cardiac events. Thus, in patients with known or suspected coronary artery disease and good exercise tolerance, the addition of thallium-201 imaging in patients with an abnormal exercise electrocardiogram provides useful prognostic information.(ABSTRACT TRUNCATED AT 250 WORDS)