Identification of severe coronary artery disease in patients with a single abnormal coronary territory on exercise thallium-201 imaging: the importance of clinical and exercise variables

Screening for asymptomatic coronary heart disease in the young 'at risk' population: Who and how?

Deaths due to coronary heart disease (CHD) remain high worldwide, despite recent achievements. An effective screening strategy may improve outcomes further if implemented in a high or ‘at risk’ cohort. Asymptomatic CHD in the young maybe underappreciated and applying an effective screening strategy to a young cohort may lead to improved outcomes due to significant socioeconomic impact from the consequences of CHD in this sub-group. A positive family history of CHD, which is known to be associated with an increased risk of future myocardial events, could aid in identifying the ‘at risk’ young cohort.

Traditional cardiovascular risk scoring systems are in wide use but lack the sensitivity or specificity required to estimate risk in an individual. Rather their use is limited to predicting population attributable risk. Functional studies such as exercise stress tests are readily available and cost effective but do not have the required sensitivity required to suggest their use as part of a screening protocol. Coronary CT angiography has been demonstrated to have high sensitivity for the detection of CHD and therefore may be suitable for screening purposes but there are concerns regarding radiation exposure.

Here we review the evidence for the use of potential screening strategies and the suitability of using such strategies to estimate risk of CHD in a young ‘at risk’ population.

Intracoronary pressure and flow velocity for hemodynamic evaluation of coronary stenoses

Adequate patient selection for percutaneous coronary intervention is of utmost importance to minimize early and late complications. Consequently, objective evidence for myocardial ischemia is mandatory for the management of patients with coronary artery disease, in particular in multivessel disease and intermediate lesions (40-70% diameter stenosis on angiography). The use of sensor-equipped guide wires for the assessment of functional coronary lesion severity has become widespread in the catheterization laboratory. The indices derived from pressure or flow measurements, fractional flow reserve, coronary flow velocity reserve and relative coronary flow velocity reserve show a high agreement with noninvasive stress testing. However, while these indices are based on either intracoronary pressure or flow, they do not investigate the hemodynamics of the coronary circulation entirely, leading to ambiguous outcomes. Only the use of simultaneously measured pressure and flow will avoid any possible misinterpretation of the data.

Single-photon emission computed tomography myocardial perfusion imaging in the diagnosis of left main disease

BACKGROUND

Left main disease (LMD), defined as > or = 50% lesion stenosis, occurs in 3% to 5% of patients undergoing catheterization. Limited data on the value of single-photon emission computed tomography (SPECT) imaging for diagnosis of LMD exists.

HYPOTHESIS

This study sought to evaluate the diagnostic accuracy of SPECT imaging in the diagnosis of LMD.

METHODS

A total of 74 consecutive patients with LMD, identified from our catheterization lab database (January 2003-December 2007) with gated exercise (15 patients) or adenosine (59 patients), thallium 201, or Tc-99m SPECT imaging within 6 months of index angiography were included. Group 1 (Gp 1) included 33 patients with isolated LMD. Group 2 (Gp 2) consisted of 41 patients with LMD and 1-vessel disease (6); LMD and 2-vessel disease (24); and LMD and 3-vessel disease (11).

RESULTS

Reversible perfusion defects (PD) were absent in 6 (18%) of Gp 1 and 8 (20%) of Gp 2 patients. Among Gp 1 patients, PD in 1-vessel, 2-vessel, 3-vessel distribution were seen in 20 (61%), 5 (15%), and 2 (6%) patients respectively. In comparison, PD in 1-vessel, 2-vessel, 3-vessel distribution were observed in 20 (49%), 12 (29%), and 1 (2%) of Gp 2 patients respectively. Left main (LM) pattern was noted in 6 patients (Gp 1: 2, Gp 2: 4). Transient ischemic dilatation (TID) was encountered in 34 patients (Gp 1: 17, Gp 2: 17) and in 4 patients with normal perfusion scans.

CONCLUSIONS

These data represent the largest analysis of patients with "isolated" LMD. Approximately 19% of patients with LMD have no reversible PD on SPECT. While LM pattern is rare, 1-vessel distribution PD and TID represent the most frequent SPECT abnormalities.

Computed tomographic coronary angiographic assessment of high-risk coronary anatomy in patients with suspected coronary artery disease and intermediate pretest probability

BACKGROUND

It is unclear if computed tomographic coronary angiography (CTA), an evolving technique for the evaluation of coronary artery disease (CAD), can identify patients with high-risk coronary anatomy.

METHODS

Among patients referred for invasive angiography at Hamilton Health Sciences (Hamilton, Ontario, Canada), those with an intermediate pretest probability (25%-60% likelihood of a significant stenosis) were prospectively identified using a multivariate risk score and were studied on a 64-detector Toshiba Aquilion scanner (Toshiba Medical Systems, Tokyo, Japan) before invasive angiography. Patients with high-risk anatomy (left main, 3-vessel CAD, or 2-vessel CAD involving the proximal left anterior descending artery) or at least 1 significant stenosis were identified on CTA and invasive angiography, and the results of these modalities were compared on a per patient basis.

RESULTS

Eighty patients were enrolled in the study (mean age 56 +/- 9 years, male-female ratio 43:37). Nondiagnostic scan results were obtained in 5 patients (6%). By CTA, 13 patients had high-risk anatomy and 31 patients had at least 1 significant stenosis. For the per patient detection of high-risk anatomy, CTA had 100% sensitivity (95% CI 69%-100%), 95% specificity (95% CI 86%-95%), a positive likelihood ratio of 18.0 (95% CI 6.4-50.3), and a negative likelihood ratio of 0.05 (95% CI 0-0.072). Revascularization was performed in 100% of patients with high-risk anatomy on CTA, 83% with at least 1 significant stenosis on CTA, and 0% without a significant stenosis on CTA.

CONCLUSION

In appropriately selected patients, CTA is a highly sensitive and specific technique for the detection of high-risk anatomy and maybe a valuable method for noninvasive risk stratification.

Left main coronary artery stenosis: state-of-the-art

Patients with stenosis of the left main coronary artery present difficult challenges. The risks associated with this lesion have been known since the early days of angiography when patients were found to have increased mortality during follow-up. This information led to the general guidelines that surgical revascularization should be considered the treatment of choice in patients with significant left main coronary artery stenosis. Current advances in invasive cardiology have brought important information to the field. Intravascular ultrasound is now used routinely to evaluate angiographically indeterminate lesions with criteria now set forward as to what constitutes an indication for revascularization. Stents have even further dramatically changed the landscape. There are substantial issues, however, that need to addressed. These include the following: (1) the effect of specific lesion location on outcome - it is known that patients with distal bifurcation left main disease have worse outcome; (2) the potential for subacute thrombosis of the left main coronary artery; (3) the impact of left ventricular function and patient comorbidities irrespective of the degree and location of left main coronary artery stenosis; and (4) the risk-benefit ratio of stenting versus coronary artery bypass graft surgery. These issues are currently being addressed in two seminally important trials including the SYNTAX trial, which randomizes patients with left main and/or three-vessel disease to either coronary artery bypass graft surgery or a TAXUS drug-eluting stent. This trial is in the final stages of patient recruitment and will have important implications for the field. The other trial is the COMBAT trial, which is focused exclusively on left main coronary artery stenosis and randomizes patients with left main coronary artery disease either to a Sirolimus-eluting stent (Cypher, Johnson and Johnson Cordis, USA) or to coronary artery bypass graft surgery. The field of left main coronary artery disease continues to expand in terms of the evidence available for optimal patient evaluation and selection of treatment modalities.

The Prognostic Value of Normal Exercise Myocardial Perfusion Imaging and Exercise Echocardiography

OBJECTIVES

The purpose of this work was to determine the prognostic value of normal exercise myocardial perfusion imaging (MPI) tests and exercise echocardiography tests, and to determine the prognostic value of these imaging modalities in women and men.

BACKGROUND

Exercise MPI and exercise echocardiography provide prognostic information that is useful in the risk stratification of patients with suspected coronary artery disease (CAD).

METHODS

We searched the PubMed, Cochrane, and DARE databases between January 1990 and May 2005, and reviewed bibliographies of articles obtained. We included prospective cohort studies of subjects who underwent exercise MPI or exercise echocardiography for known or suspected CAD, and provided data on primary outcomes of myocardial infarction (MI) and cardiac death with at least 3 months of follow-up. Secondary outcomes (unstable angina, revascularization procedures) were abstracted if provided. Studies performed exclusively in patients with CAD were excluded.

RESULTS

The negative predictive value (NPV) for MI and cardiac death was 98.8% (95% confidence interval [CI] 98.5 to 99.0) over 36 months of follow-up for MPI, and 98.4% (95% CI 97.9 to 98.9) over 33 months for echocardiography. The corresponding annualized event rates were 0.45% per year for MPI and 0.54% per year for echocardiography. In subgroup analyses, annualized event rates were <1% for each MPI isotope, and were similar for women and men. For secondary events, MPI and echocardiography had annualized event rates of 1.25% and 0.95%, respectively.

CONCLUSIONS

Both exercise MPI and exercise echocardiography have high NPVs for primary and secondary cardiac events. The prognostic utility of both modalities is similar for both men and women.

Identification of advanced coronary artery disease with exercise myocardial perfusion imaging: the clinical value of a novel approach for assessing lung thallium-201 uptake

INTRODUCTION

The precise clinical utility of lung 201Tl uptake in exercise SPECT myocardial perfusion imaging remains open to research. This study validates an optimal index for lung 201Tl uptake measurement and assesses its value in the prediction of higher-risk coronary artery disease (CAD).

METHOD

Three hundred and ninety-eight patients underwent exercise SPECT myocardial perfusion imaging. They were separated into derivation (n = 217) and validation (n = 186) groups, both including sub-populations of lower- and higher-risk CAD, according to coronary angiography. Another 56 individuals with a low probability of CAD comprised the control group. From a planar, anterior, post-exercise acquisition, the lung (L) to heart (H) maximal (L/H(max)), total (L/H(mean)) and background-subtracted total (L/H(net)) ratios were calculated. These were also adjusted for confounding variables, as assessed from the control group. ROC analysis was used to compare the L/H ratios and define thresholds of abnormality. The performance of the optimal index was assessed in the derivation group and was then tested in the validation population. Subsequently, it was compared with other scintigraphic, exercise electrocardiography and clinical variables.

RESULTS

In the derivation group L/H(net) was a better discriminator for higher-risk CAD than both L/H(max) and L/H(mean). Similarly, the adjusted L/H(net) was a better discriminator than both the adjusted L/H(max) and the adjusted L/H(mean). No significant difference was attained between L/H(net) and the adjusted L/H(net). At the upper defined threshold of abnormality, sensitivity and specificity of L/H(net) in the detection of higher-risk CAD in the derivation and the validation cohorts were 52% and 92% versus 47% and 94%, respectively (p = ns). The results were similar at other defined thresholds. Moreover, L/H(net) was found to be a significant predictor of higher-risk CAD, superior to myocardial perfusion images, transient ventricular dilation measurements, and clinical and exercise testing variables (ROC analysis and logistic regression). By raising the threshold of abnormality of L/H(net), specificity and positive predictive value increased, whereas sensitivity and negative predictive value decreased.

CONCLUSION

Lung 201Tl assessment assists substantially in the identification of higher-risk CAD in exercise SPECT myocardial perfusion imaging and this is best achieved by L/H(net). This index is a significant predictor of higher-risk CAD, superior to myocardial perfusion images, and its value is associated with the probability of a disease state.

Correspondence between left ventricular 17 myocardial segments and coronary arteries

AIMS

The last guidelines recommend a standardized 17-segment model for tomographic imaging of the left ventricle. The aim of this study is to analyse the correspondence of the 17 left ventricular segments with each coronary artery by myocardial perfusion SPECT studies.

METHODS AND RESULTS

Fifty patients selected for percutaneous revascularization of one coronary artery [24 left anterior descending (LAD), 15 right coronary artery (RCA), and 11 left circumflex (LCX)] were included. The (99m)Tc-labelled compound was injected immediately after the inflation of the balloon during percutaneous coronary angioplasty. At least 90 s of complete occlusion time was required. Maximal contour of regions of hypoperfusion corresponding to each coronary artery occlusion were delineated over the polar map of 17 segments. Nine segments corresponded to only one coronary artery: eight to LAD (basal anterior, basal anteroseptal, mid-anterior, mid-anteroseptal, apical anterior, apical septal, apical lateral, and apex) and one to LCX (basal anterolateral). Basal inferoseptal, mid-inferoseptal, and apical inferior segments could correspond to LAD or RCA. Basal inferior, basal inferolateral, mid-inferior, and mid-inferolateral segments could correspond to RCA or LCX, whereas the mid-anterolateral segment could correspond to LAD or LCX.

CONCLUSION

The most specific segments (anterior, anteroseptal, and all apical segments except the infero-apical) correspond to LAD but no segment can be exclusively attributed to the RCA. Inferoseptal segments can be attributed to LAD or RCA, inferior and inferolateral segments to RCA or LCX, and mid-anterolateral segment to LAD or LCX.

Electrocardiographic prediction of the severity of posterior wall perfusion defects on rest technetium-99m Sestamibi myocardial perfusion imaging

To identify electrocardiogram (ECG) variables predicting the severity of previous posterior wall myocardial infarction as measured by technetium-99m-Sestamibi rest single-photon emission computed tomography, we assessed agreement between ECG criteria and posterior wall perfusion defects (PWPDs) in 236 patients. Established ECG criteria for posterior and posterolateral infarctions were present in 22% and 19% of patients, respectively, and did not predict severity of PWPD ( P = NS). Univariate predictors of severity were the Selvester QRS score (SQS) ( P = .001) and an upright T wave in V 1 (UTV 1 ) greater than 0.2 mV ( P = .001). Regression analysis demonstrated that SQS ( P = .0001) and UTV 1 greater than 0.2 mV ( P = .006) were highly predictive of severity ( c statistic = 0.793). All severe PWPDs had an SQS of 2 or higher. Established ECG patterns for diagnosis of posterior infarction are insensitive and poor predictors of severity. The SQS and UTV 1 are effective for the diagnosis of posterior infarction and useful for the estimation of infarct severity.

Prognostic value of coronary blood flow velocity and myocardial perfusion in intermediate coronary narrowings and multivessel disease

OBJECTIVES

This study aimed to investigate the roles of intracoronary derived coronary flow velocity reserve (CFVR) and myocardial perfusion scintigraphy (single photon emission computed tomography, or SPECT) for management of an intermediate lesion in patients with multivessel coronary artery disease.

BACKGROUND

Evaluation of the functional significance of intermediate coronary narrowings (40% to 70% diameter stenosis) is important for clinical decision making and risk stratification.

METHODS

In a prospective, multicenter study, SPECT was performed in 191 patients with stable angina and multivessel disease and scheduled for angioplasty (percutaneous transluminal coronary angioplasty, or PTCA) of a severe coronary narrowing. Coronary flow velocity reserve was determined selectively distal to an intermediate lesion in another artery using a Doppler guidewire. Percutaneous transluminal coronary angioplasty of the intermediate lesion was deferred when SPECT was negative or CFVR greater-than-or-equal 2.0. Patients were followed for one year to document major cardiac events (death, infarction, revascularization), related to the intermediate lesion.

RESULTS

Reversible perfusion defects were documented in the area of the intermediate lesion in 30 (16%) patients; CFVR was positive in 46 (24%) patients. Percutaneous transluminal coronary angioplasty of the intermediate lesion was deferred in 182 patients. During follow-up, 19 events occurred (3 myocardial infarctions, 16 revascularizations). Coronary flow velocity reserve was a more accurate predictor of cardiac events than was SPECT; relative risk: CFVR 3.9 (1.7 to 9.1), p < 0.05; SPECT 0.5 (0.1 to 3.2), p = NS. Multivariate analysis revealed CFVR as the only significant predictor for cardiac events.

CONCLUSIONS

Deferral of PTCA of intermediate lesions in multivessel disease is safe when CFVR greater-than-or-equal 2.0 (event rate 6%). This selective evaluation of coronary lesion severity during cardiac catheterization allows a more accurate risk stratification than does SPECT, which is important for clinical decision making in this patient cohort.

Usefulness of fractional flow reserve for risk stratification of patients with multivessel coronary artery disease and an intermediate stenosis

Intracoronary-derived, pressure-based fractional flow reserve (FFR) is important for clinical decision-making in patients with 1-vessel coronary artery disease (CAD). In the present study, we investigated the prognostic value of FFR in patients with intermediate stenoses and multivessel CAD. Therefore, we analyzed 107 patients with stable angina pectoris who underwent myocardial perfusion scintigraphy and showed no perfusion defects in the region of the intermediate lesion. At angiography, FFR was determined distal to the intermediate lesion. FFR was abnormal (i.e., <0.75) in 15 of 107 stenoses (14%). Angioplasty of the intermediate stenosis was deferred based on the absence of a perfusion defect. Patients were followed for 1 year to document major cardiac events related to the intermediate lesion. At 1-year follow-up, a total of 12 (11%: no deaths, 3 myocardial infarctions, 2 coronary bypass operations, 7 coronary angioplasties) events occurred in the entire group that were related to the intermediate lesion. The event rate was significantly higher when angioplasty was deferred despite FFR <0.75 compared with the group with FFR > or = 0.75 (4 of 15 [27%] vs 8 of 92 [9%]; p <0.041). The relative risk of FFR for predicting cardiac events (mainly revascularization procedures) was 3.1 (95% confidence interval 1.1 to 8.9; p <0.05). In conclusion, deferral of angioplasty of intermediate coronary narrowings is safe based on FFR > or = 0.75 in this patient cohort; this coincides with previous reports in patients with 1-vessel CAD. Furthermore, these results suggest that FFR is more useful than single-photon emission computed tomography for clinical decision-making and risk stratification in patients with multivessel CAD.

Adequate patient selection for coronary revascularization: an overview of current methods used in daily clinical practice

Widely used non-invasive stress modalities, like exercise ECG, MPS and stress-echocardiography, are the tests of first choice for the diagnosis of CAD. It has been shown in numerous studies that non-invasive assessment of perfusion abnormalities is an adequate strategy for risk stratification. Moreover, non-invasive stress testing should be performed before a diagnostic cardiac catheterization to document the presence of myocardial ischemia, as a prerequisite for coronary revascularization. Coronary angiography is the gold standard for identifying CAD; however this technique is limited in assessing functional severity of coronary narrowings ('illusion of luminology'; see also Figure 5). The recently introduced i.c. hemodynamic parameters (CFVR and FFR) can identify functional severity of specific lesions and have shown a good agreement with the results of non-invasive stress test in validation studies. Furthermore, there is accumulating evidence that it is safe to defer a PTCA procedure, based on normal FFR and CFVR values. As these indices are derived during an invasive cardiac catheterization procedure, its use is recommended during a so called 'ad hoc' PTCA setting. Furthermore, they are particularly useful for clinical decision making in patients with documented multivessel CAD, as both indices allow selective evaluation of coronary narrowings in different arteries. Revascularization procedures are costly and always have a potential risk. It is important to be aware that, using above mentioned methods, unnecessary interventions (lacking potential benefit) may be avoided.