Angiographically silent left main disease detected by intravascular ultrasound: a marker for future adverse cardiac events

Revascularization Options for Left Main Disease: What Clinicians Need to Know

PURPOSE OF REVIEW

Left main disease represents the highest-risk lesion subset of coronary artery disease and is associated with adverse cardiovascular events. Accordingly, we aim to understand how the significance of left main disease is assessed by different modalities, followed by a review of management options in current era.

RECENT FINDINGS

Invasive coronary angiogram remains the gold standard for assessment of left main disease, but intracoronary imaging or physiological testing is indicated for angiographically equivocal disease. Revascularization by either coronary artery bypass surgery or percutaneous coronary intervention is strongly recommended, which have been compared by six randomized trials, as well as recent meta-analyses. Surgical revascularization remains the preferred mode of revascularization, especially in patients with high lesion complexity and left ventricular dysfunction. Randomized studies are needed to understand if current-generation stents with the use of intracoronary imaging and improved medical therapy could match outcomes with surgical revascularization.

Prognostic Significance of Nonobstructive Left Main Coronary Artery Disease in Patients With and Without Diabetes: Long-Term Outcomes From the CONFIRM Registry

BACKGROUND

Prognostic significance of non-obstructive left main (LM) disease was recently reported. However, the influence of diabetes mellitus (DM) on event rates in patients with and without non-obstructive LM disease is not well-known.

METHODS

We evaluated 27,252 patients undergoing coronary computed tomographic angiography from the COroNary CT Angiography Evaluation For Clinical Outcomes: An InteRnational Multicenter (CONFIRM) Registry. Cumulative long-term incidence of all-cause mortality (ACM) was assessed between DM and non-DM patients by normal or non-obstructive LM disease (1-49% stenosis).

RESULTS

The mean age of the study population was 57.6±12.6 years. Of the 27,252 patients, 4,434 (16%) patients had DM. A total of 899 (3%) deaths occurred during the follow-up of 3.6±1.9. years. Compared to patients with normal LM, those with non-obstructive LM had more pronounced overall coronary atherosclerosis and more cardiovascular risk factors. After clinical risk factors, segment involvement score, and stenosis severity adjustment, compared to patients without DM and normal LM, patients with DM were associated with increased ACM regardless of normal (HR 1.48, 95% CI 1.22-1.78, p<0.001) or non-obstructive LM (HR 1.46, 95% CI 1.04-2.04, p=0.029), while nonobstructive LM disease was not associated with increased ACM in patients without DM (HR 0.85, 95% CI 0.67-1.07, p=0.165) and there was no significant interaction between DM and LM status (HR 1.03, 95% CI 0.69-1.54, p=0.879).

CONCLUSION

From the CONFIRM registry, we demonstrated that DM was associated with increased ACM. However, the presence of non-obstructive LM was not an independent risk marker of ACM, and there was no significant interaction between DM and non-obstructive LM disease for ACM.

Assessment of left main coronary artery disease: a comparison between invasive and noninvasive

Left main coronary artery disease has significant therapeutic as well as prognostic implications. The presence of left main coronary artery stenosis is strongly associated with poor short- and long-term prognoses. Accurate identification of left main stenosis is extremely important since it would be the main factor to guide management. There are several modalities used to determine the presence of atherosclerosis and the degree of stenosis in a left main coronary artery. Newer modalities allow for an accurate evaluation of left main stenosis and atherosclerosis. In this review, we go through different invasive and noninvasive modalities to diagnose left main stenosis, shedding more light into coronary computed tomography angiography, and its accuracy in this specific diagnosis.

Outcomes of Unprotected Left Main Percutaneous Coronary Intervention: A Single-Centre Experience

Introduction

When the baseline anatomical syntax score-I (SxSI) is more than or equal to 33, percutaneous coronary intervention (PCI) of unprotected left main (UPLM) is discouraged and considered as high-risk of adverse cardiac events. We designed this study to compare the outcomes of UPLM-PCI between the low to intermediate-syntax score (SxSI^low/^int.) group (defined as SxSI <33) and the high-syntax score (SxSI^high) group (defined as SxSI more than or equal 33) with a subanalysis to explore the predictive role of intravascular images (IVI).

Methods

The study is a retrospective observational analysis in a prospective cohort. The prospectively gathered data of consecutive patients, who were enrolled from January 2018 to December 2018, were analyzed at 1-year regarding the primary outcome of major adverse cardiovascular and cerebrovascular events (MACCE). An independent committee calculated the SxSI and reviewed all the events.

Results

Baseline data of 2144 patients were considered for analysis. 1245 underwent PCI and 32 (2.57%) had PCI of UPLM; of these, 24 (75%) were in SxSI^low/^int. group and 8 (25%) in SxSI^high group. The mean SxSI was 20.3 ± 6.5 and 37.1 ± 4.9 for SxSI^low/^int. and SxSI^high groups, respectively. Compared with patients in the SxSI^low/^int., patients in SxSI^high group had a greater syntax score-II (<0.0001), which reflects the expected 4-year mortality after PCI by combining the SxSI and clinical variables.Interestingly, despite the fact that the proportion of subjects who sustained MACCE was almost three times more among the SxSIhigh compared to their SxSIlow/int. counterparts [1 (12.5%) vs. 1 (4.2%), P = 0.444], this difference was not statistically significant.It was noted that a higher proportion of patients in whom intravascular imaging (IVI) was not used to guide PCI sustained MACCE compared with that in whom IVI was utilized (2 [50%] vs. [0%], P = 0.012). There is a strong, negative, statistically significant association between the use of IVI and the occurrence of MAACE (Phi=-0.681), which reflects that the use of imaging is associated with significantly lower probability of developing MACCE.

Conclusion

As demonstrated in this real-world cohort, PCI of UPLM provides excellent outcome at one year regardless of the initial anatomical syntax score. Furthermore, it appears that IVI utilization during the index PCI procedure of UPLM is a potent and independent predictor of MACCE.

Lipid-rich large plaques in a non-culprit left main coronary artery and long-term clinical outcomes

BACKGROUND

An integrated backscatter (IB) intravascular ultrasound (IVUS) provides an information about tissue components and vulnerability of coronary plaques. The presence of vulnerable plaque in non-culprit lesion is associated with future clinical events. The purpose of this study was to assess the association between the characteristics of non-culprit left main coronary artery (LMCA) plaques evaluated by IB-IVUS and long-term clinical outcomes in patients undergoing percutaneous coronary intervention (PCI).

METHODS

Among the patients who underwent non-LMCA PCI, we studied 366 patients with adequate LMCA IVUS images. Conventional and IB-IVUS analyses of the LMCA segment were performed. Lipid-rich large plaque was defined as the presence of both a lager plaque volume and a higher percentage of the lipid component than the obtained median values. Major adverse cardiovascular events (MACE) included cardiac death, myocardial infarction, and unplanned revascularization.

RESULTS

The mean age of the patients was 68.5 ± 10.2 years, 79.8% were men. Median follow-up period was 6.0 years (IQR: 4.2-8.1 years). The incidence of MACE was significantly higher in patients with lipid-rich large plaques (P = .006). The incidence rates of cardiac death, myocardial infarction, and unplanned revascularization were significantly higher in patients with lipid-rich large plaques (P = .02, 0.004, and 0.02, respectively). Multivariate Cox regression analysis showed that the presence of a lipid-rich large plaque was significantly associated with MACE (HR: 1.74; 95%CI: 1.17-2.58; P = .006).

CONCLUSION

The presence of lipid-rich large plaques in a non-culprit LMCA can be associated with the long-term MACE in patients who have undergone PCI.

Clinical Impact of Circulating Irisin on Classified Coronary Plaque Characteristics

BACKGROUND

Myokines are hormones secreted by skeletal muscles during physical activity. Low myokine levels may contribute to metabolic dysfunction and cardiovascular disorders. Irisin, a newly identified myokine, has been the focus of recent research. The aim of the present study was to analyze the association between circulating irisin levels and tissue characteristics of nonculprit left main coronary artery (LMCA) plaques with the use of integrated backscatter (IB) intravascular ultrasound (IVUS).

METHODS

This observational study enrolled 55 Japanese patients following successful percutaneous coronary intervention for lesions in the left anterior descending arteries or left circumflex arteries. Circulating myokine levels, including myostatin, brain-derived neurotrophic factor, and irisin, were measured by an enzyme-linked immunosorbent assay. Tissue characteristics of LMCA plaque were evaluated by IB-IVUS.

RESULTS

Circulating irisin levels were negatively associated with percent lipid volume (%LV) [r = -0.31 (95% CI, -2.52 to -0.21), P = 0.02] and positively associated with percent fibrous volume (%FV) [r = 0.32 (95% CI, 0.22-2.20), P = 0.02]. The optimal cutoff value of circulating irisin for the prediction of lipid-rich LMCA plaques was 6.02 μg/mL [area under the curve = 0.713, P < 0.01 (95% CI, 0.58-0.85)]. Multivariate linear regression analysis identified circulating irisin levels as independent predictors for %LV and %FV of the LMCA [β = -0.29 (95% CI, -2.53 to -0.07), P = 0.04 and β = 0.30 (95% CI, 0.10-2.23), P = 0.03, respectively].

CONCLUSIONS

Circulating irisin levels are significantly associated with tissue characteristics of nonculprit LMCA plaques.

Assessing the left main stem in the cardiac catheterization laboratory. What is "significant"? Function, imaging or both?

Revascularization of significant Left Main Stem (LMS) disease improves clinical outcomes. This can be achieved through either Coronary Artery Bypass Grafting or Percutaneous coronary intervention. Defining a significant stenosis of the LMS can be challenging and debatable, as most data have been derived using angiographic assessment alone, with a threshold of 50% luminal stenosis used as a marker of functional significance. The use of adjunctive technologies like Intravascular Ultrasound and Fractional Flow Reserve has improved our ability to accurately assess the anatomical severity and physiological significance of coronary artery stenoses, much more so, than can be achieved through conventional angiography alone. An improved assessment of LMS disease through these adjunctive techniques offers procedural and clinical benefits. Rather than focus on the preferred methods of revascularisation, this article aims to highlight the common pitfalls and misconceptions in the assessment of LMS stenoses. We also propose a simple algorithm for the assessment of LMS disease to help guide revascularisation decisions.

Interventional Management of Unprotected Left Main Coronary Artery Disease: Patient Selection and Technique Optimization

For many years, coronary artery bypass graft surgery has been the gold standard for revascularization of patients with left main disease; however, increasing evidence suggests that percutaneous coronary intervention with drug-eluting stents may be an acceptable alternative or even preferred in select cases. This review will present clinical evidence examining the outcomes of drug-eluting stents compared to coronary artery bypass graft surgery for unprotected left main coronary artery disease and discuss the anatomic factors, patient variables, and clinical strategies that may dictate choice of revascularization modality for patients with left main disease. If percutaneous coronary intervention is selected to treat unprotected left main disease, meticulous technique is essential to optimize outcomes, including use of procedural physiology and imaging guidance, optimal stent and adjunct pharmacology use, and expert management of the distal bifurcation. Finally, issues of equipoise and uncertainty are identified, representing areas for future investigation.

Intravascular Ultrasound for the Diagnosis and Treatment of Left Main Coronary Artery Disease

Limitations of angiography for assessment of coronary artery disease are well-known, but are more evident and relevant in the left main coronary artery (LMCA) segment given the amount of myocardium this vessel subtends and the risks associated with the presence of atherosclerosis and subsequent intervention. Intravascular ultrasound (IVUS) characterizes the severity of luminal narrowing, plaque morphology, and plaque extension into the distal bifurcation. Once the indication for percutaneous intervention (PCI) is established, information provided by IVUS is crucial to plan treatment and optimize results. IVUS-guided PCI with drug-eluting stents improves clinical outcomes, particularly in patients with distal left main disease.

Sex differences in the visual-functional mismatch between coronary angiography or intravascular ultrasound versus fractional flow reserve

OBJECTIVES

This study sought to assess differences in visual-functional mismatches between men and women.

BACKGROUND

Sex differences in mismatch between coronary anatomy and function remain poorly understood.

METHODS

We assessed quantitative coronary angiography, intravascular ultrasound (IVUS), fractional flow reserve (FFR), and echocardiographic left ventricular mass in a prospective cohort of 700 patients (493 male and 207 female patients) with 700 left anterior descending coronary lesions.

RESULTS

The female patients were older than the male patients (64 ± 10 years vs. 60 ± 10 years, p < 0.001) and body surface area (BSA) (57 ± 0.13 m(2) vs. 1.79 ± 0.13 m(2), p < 0.001) and left ventricular mass (151 ± 37g vs. 171 ± 41 g, p < 0.001) were smaller. Although there were no sex differences in angiographic diameter stenosis, lesion length, and IVUS minimal lumen area (MLA), FFR was higher in female patients (0.83 ± 0.09 vs. 0.79 ± 0.09, p < 0.001). Female patients had a smaller reference vessel area (11.4 ± 3.3 mm(2) vs. 13.1 ± 4.0 mm(2)), vessel area (9.0 ± 3.3 mm(2) vs. 11.1 ± 4.2 mm(2)), and plaque burden (69.8 ± 13.7% vs. 73.8 ± 12.2%) at the MLA site compared with male patients (all p < 0.001). To predict FFR <0.80, angiography had a lower positive predictive value in female patients (44% vs. 60%, p = 0.014); this was also seen in the IVUS analysis. Unlike angiography, the IVUS-MLA had a lower concordance rate in female patients (64% vs. 71%, p = 0.046). Independent predictors of FFR were age, BSA, lesion length, angiographic diameter stenosis, and IVUS-MLA and plaque burden. When left ventricular mass was included, it also predicted FFR, replacing BSA.

CONCLUSIONS

In female patients with smaller BSA, left ventricular mass, and vessel size, smaller myocardial territory may be responsible for the higher FFR value for any given stenosis compared with male patients. Considering the higher rate of visual-functional mismatch, FFR-guided decision making is especially important in female patients to avoid unnecessary procedures. (Natural History of FFR-Guided Deferred Coronary Lesions [IRIS FFR-DEFER Registry]; NCT01366404).

Percutaneous revascularization of left main: role of imaging, techniques, and adjunct pharmacology

Refinement of interventional techniques, adjunctive pharmacological therapy, and the introduction of drug-eluting stents have fostered new interest for the percutaneous treatment of unprotected left main coronary artery (ULMCA) stenosis. Several observational registries, some randomized trials and several meta-analyses have consistently shown no difference in mortality and myocardial infarction between percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery in patients with ULMCA stenosis, but a higher rate of target vessel revascularization in patients treated with PCI. As a consequence, PCI of ULMCA stenosis has been upgraded to class IIa or IIb indication in the current European or American practice guidelines. However, several critical issues should be properly addressed when pursuing a percutaneous strategy for the treatment of ULMCA stenosis, such as the use of IVUS for procedural guidance, assessment of disease location, optimal technique for distal ULMCA stenosis, risk of stent thrombosis, optimal duration of dual antiplatelet therapy, and the most appropriate strategy for post-procedure follow up. Multidisciplinary team approach remains essential to provide a balanced information to the patient and to offer the beast treatment option.

Impact of the low- to high-density lipoprotein cholesterol ratio on composition of angiographically ambiguous left main coronary artery plaque

BACKGROUND

A high low-density lipoprotein cholesterol (LDL-C) to a high-density lipoprotein cholesterol (HDL-C) ratio is associated with cardiac events, while the left main coronary artery (LMCA) is considered to be an important target of atherosclerotic plaque accumulation. This aim of the present study was to investigate the relationship between a LDL-C/HDL-C ratio and the characteristics of tissue components of LMCA plaque.

METHODS AND RESULTS

One-hundred-twenty consecutive patients with stable angina pectoris who received chronic statin treatment underwent percutaneous coronary intervention for the left coronary artery. We prospectively performed integrated backscatter (IB) intravascular ultrasound (IVUS) to their LMCAs and evaluated the tissue characteristics. According to the median value of their LDL-C/HDL-C ratios (2.4), they were divided into 2 groups [high LDL-C/HDL-C ratio (>2.4) (n=60) or low LDL-C/HDL-C ratio (≤ 2.4) (n=60)]. There was no significant difference in the data analyzed using conventional IVUS between the 2 groups. In the IB-IVUS analysis, patients with a high LDL-C/HDL-C ratio had a larger lipid volume and a smaller fibrous volume compared to patients with a low LDL-C/HDL-C ratio (52 ± 10% vs. 48 ± 10%, P=0.014 and 45 ± 9% vs. 50 ± 10%, P=0.010).

CONCLUSIONS

A high LDL-C/HDL-C ratio was associated with a high percentage of lipid volume and a low percentage of fibrous volume in LMCA lesions. Our findings might well suggest the increased risk of cardiovascular events in patients with a high LDL-C/HDL-C ratio.

PPAR-γ agonism for cardiovascular and renal protection

Diabetes mellitus is an established risk factor for cardiovascular disease and the leading cause of end-stage renal disease in the Western World. Thiazolidinediones (TZDs) represent a class of antidiabetic agents that exert their glucose-lowering effects by reducing insulin resistance, through stimulation of a type of nuclear receptor, called peroxisome proliferator-activated receptor-γ. Apart from improving glycemic control, TZDs were shown to exert beneficial effects on several components of the metabolic syndrome and cardiovascular risk markers. Furthermore, background and human studies have shown that TZDs reduce urinary albumin and protein excretion and interfere with most of the pathogenentic pathways involved in the development and progression of diabetic nephropathy. On the other hand, currently used TZDs have side effects, most important of which is fluid retention leading to wait gain and heart failure deterioration. With regards to cardiovascular outcomes, the anticipated benefit of TZDs was demonstrated for pioglitazone, whereas a series of previous meta-analyses linking rosiglitazone treatment with increased risk of myocardial infarction and cardiovascular death raised uncertainty around the cardiovascular safety of rosiglitazone. This article will discuss the effects of TZDs on established and emerging cardiovascular risk factors, the data on possible beneficial renal effects of these compounds, and the existing evidence from large-scale clinical trials and meta-analyses on their effects on cardiovascular outcomes, aiming to provide an overview of the cardio- and renoprotective properties of these drugs.

Intravascular Ultrasound Classification of Plaque Distribution in Left Main Coronary Artery Bifurcations

Background— Angiographic classifications of the location and severity of disease in the main vessel and side branch of coronary artery bifurcations have been proposed and applied to distal left main coronary artery (LMCA) bifurcation.

Methods and Results— We reviewed 140 angiograms of distal LMCA and ostial left anterior descending (LAD) and left circumflex (LCX) artery lesions with preintervention intravascular ultrasound (IVUS) of both the LAD and LCX arteries as well as the LMCA. Of 140 patients, 92.9% had at least 1 cross section with ≥40% IVUS plaque burden versus 57.2% of patients with an angiographic diameter stenosis ≥50%. Contrary to angiographic classifications, IVUS showed that bifurcation disease was rarely focal and that both sides of the flow divider were always disease-free. Continuous plaque from the LMCA into the proximal LAD artery was seen in 90%, from the LMCA into the LCX artery in 66.4%, and from the LMCA into both the LAD and LCX arteries in 62%. Plaque localized to either the LAD or LCX ostium and not involving the distal LMCA was seen in only 9.3% of LAD arteries and 17.1% of LCX arteries. Plaque distribution was not influenced by the LAD/LCX angiographic angle, lesion severity, LMCA length, or remodeling. We proposed an IVUS classification for bifurcation lesions illustrating longitudinal and circumferential spatial plaque distribution.

Conclusions— Angiographic classification of LMCA bifurcation lesions is rarely accurate. IVUS shows that the carina is always spared and that the disease is diffuse rather than focal.

Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180466.

Rationale and approach to evaluation of the impact of medical therapies on progression of atherosclerosis with arterial wall imaging

BACKGROUND

Despite the benefit of medical therapies, there remains a substantial residual risk of cardiovascular events. Atherosclerosis imaging has been used to assess new therapies.

SCOPE

A selective review of current imaging techniques used to evaluate novel anti-atherosclerotic therapies.

FINDINGS

Noninvasive and invasive arterial wall imaging permits characterization of the quantity and composition of atherosclerotic plaque. Serial imaging enables assessment of the impact of therapies on the natural history of disease progression.

CONCLUSION

Both noninvasive and invasive imaging modalities can be used in development programs to provide an early assessment of the impact of novel anti-atherosclerotic agents.

Cerebral transient ischemic attack due to left ventricular thrombus formation in a young patient with silent myocardial infarction and normal coronary arteries

Among many cardiac diseases related to cerebral stroke, left ventricular thrombus formation due to silent myocardial infarction with normal coronary arteries represents a rare cause of cerebral ischemia. We describe an unusual case of cerebral ischemia due to cardiac thrombus formation in a young patient with silent myocardial infarction and normal coronary arteries in which echocardiography and cardiac MR imaging clearly showed the embolic source.

Assessment on the Prevention of Progression by Rosiglitazone on Atherosclerosis in diabetes patients with Cardiovascular History (APPROACH): study design and baseline characteristics

BACKGROUND

Rosiglitazone, a thiazolidinedione, has effects on insulin sensitivity and cardiovascular risk factors that may favorably impact the progression of coronary atherosclerosis.

METHODS

APPROACH is a double-blind randomized clinical trial comparing the effects of the insulin sensitizer rosiglitazone with the insulin secretagogue glipizide on the progression of coronary atherosclerosis. Patients with type 2 diabetes and coronary artery disease undergoing clinically indicated coronary angiography or percutaneous coronary intervention are randomized to receive rosiglitazone or glipizide for 18 months using a titration algorithm designed to provide comparable glycemic control between treatment groups. The primary end point is change in percent atheroma volume from baseline to study completion in a nonintervened coronary artery, as measured by intravascular ultrasound. Cardiovascular events are adjudicated by an end point committee.

RESULTS

A total of 672 patients were randomized. The mean age was 61 years, hemoglobin A(1c) (HbA(1c)) 7.2%, body mass index 29.5 kg/m(2), and median duration of diabetes 4.8 years. At baseline, approximately half of the participants were receiving oral antidiabetic monotherapy (53.9%) with 27.5% receiving dual combination therapy and 17.9% treated with diet and exercise alone. Approximately two thirds of the participants (68%) had dyslipidemia, 79.9% hypertension, and 24% prior myocardial infarction.

CONCLUSIONS

APPROACH has fully enrolled a high-risk patient population and will compare the glucose-independent effects of rosiglitazone and glipizide on the progression of coronary atherosclerosis, as well as provide additional data on the cardiovascular safety of rosiglitazone in patients with type 2 diabetes and coronary artery disease.

Use of vascular ultrasound in clinical trials to evaluate new cardiovascular therapies

Though progress has been made in the fight against cardiovascular disease (CVD), the increasing global prevalence of cardiovascular (CV) risk factors ensures that CVD rates remain high. In order to reduce CVD incidence, a huge effort has been made to uncover additional targets for therapy and novel methods of identifying patients at risk. A low level of high-density-lipoprotein (HDL) cholesterol is recognized as an important independent risk factor for occurrence of a CV event, and new therapies capable of producing effective, clinically relevant increases in this key lipoprotein particle are in development. These therapies will most likely be assessed in comparison with proven CV-risk-reducing therapies such as statin treatment, rather than against a placebo comparator. Inevitably, therefore, clinical end-point trials will increase in both complexity and longevity. Potential efficacy data on new therapies may be revealed sooner by trials using surrogate end points, biomarkers of disease progression known to correlate with clinical events. For novel CV therapies, ultrasound-measured changes in atherosclerosis, such as the change in atheroma burden or plaque volume measured by intravascular ultrasound (IVUS), or ultrasound-measured increase in carotid intima-media thickness (CIMT), may represent useful biomarkers. Both IVUS and CIMT are being widely deployed in trials of new and existing CV therapies to assess their impact on slowing the progression of atherosclerosis, and their use in this regard is the subject of this review.

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.

Intravascular ultrasound for the evaluation of therapies targeting coronary atherosclerosis

Many cardiovascular events are clinical manifestations of underlying atherosclerotic disease. The progression of atherosclerosis, traditionally measured by angiography, is predictive of future clinical events and is a valid surrogate marker of cardiovascular (CV) disease. There is growing interest in using novel surrogate end points in clinical trials to expedite the development of new CV therapies. Innovative imaging technologies, such as intravascular ultrasound (IVUS), may carry advantages for the evaluation of coronary atherosclerotic burden and disease progression. Unlike angiography, which displays only the opacified luminal "silhouette," IVUS provides transmural imaging of the entire arterial wall and permits both detection of early-stage atherosclerosis and accurate cross-sectional and even 3-dimensional quantification of plaques. Intravascular ultrasound is now used to guide therapeutic interventions and for diagnostic purposes, primarily for the evaluation of ambiguous lesions and left main coronary artery disease. In addition, clinical studies are using IVUS serially to measure plaque progression, which appears to be related to future CV events. Although the probative force of clinical end point studies still is stronger, IVUS is catching up. Currently, several trials of CV therapies use IVUS-determined plaque progression as the end point. The rationale for using IVUS-based surrogate end points in clinical trials is discussed in the present review. Key advantages of using IVUS-based surrogate end points versus clinical outcome include smaller patient numbers and substantially shorter trial durations; this reduces costs and may expedite the development and testing of new drugs. We expect in the near future a further increase of the use of IVUS-based surrogate end points in trials that evaluate novel CV therapies targeting on coronary atherosclerosis.

The impact of cardiovascular risk factors on subclinical left main coronary artery disease: an intravascular ultrasound study

BACKGROUND

The impact of cardiovascular risk factors on subclinical but measurable left main coronary artery (LMCA) atherosclerosis is not well known.

METHODS

We analyzed 150 consecutive patients with first-time coronary artery disease presentation undergoing intervention of a left anterior descending coronary artery or left circumflex lesion with motorized intravascular ultrasound transducer pullback that included a nonstenotic LMCA. Framingham, PROCAM, and European SCORE risk assessments were determined in 107 patients <65 years of age (because the Framingham, PROCAM, and European SCORE studies excluded patients >65 years old). Intravascular ultrasound measurements were compared in patients with <10% vs 10% to 20% risk of events.

RESULTS

Plaque volumes were greater in patients with higher risk scores: P = .007 in patients with 10% to 20% PROCAM risk, P = .063 in patients with 10% to 20% Framingham risk, and P = .059 in patients with 10% to 20% SCORE risk (P = .059). The mean arc of LMCA calcium (12 degrees +/- 25 degrees overall) correlated with plaque volume (51 +/- 28 mm3, r = 0.30, P = .0001) and with the number of coronary risk factors (P = .048) and ranged from 0.28 degrees +/- 0.74 degrees in patients with 0 to 1 risk factors to 9.95 degrees +/- 21.55 degrees in patients with 2 to 4 risk factors to 19.38 degrees +/- 32.51 degrees in patients with 5 to 7 risk factors. Regression analysis showed obesity and age were the most important factors contributing to LMCA calcium.

CONCLUSION

Intravascular ultrasound measurable atherosclerosis in nonstenotic LMCA correlates with conventional primary coronary risk scores. Left main coronary artery calcium correlates both with LMCA plaque volume and risk factors. Thus, subclinical LMCA atherosclerosis may be a marker for events that are predicted by commonly used primary risk-assessment algorithms.

The Prognostic Importance of Nonsignificant Left Main Coronary Artery Disease in Patients Undergoing Percutaneous Coronary Intervention

OBJECTIVES

The purpose of this research was to study the association between nonsignificant (<50%) left main coronary artery disease (LMCAD) and short- and long-term survival in patients undergoing percutaneous coronary intervention (PCI).

BACKGROUND

The prognostic importance of nonsignificant LMCAD is unknown; however, the co-existence of nonsignificant LMCAD may influence revascularization decisions.

METHODS

We analyzed mortality and repeat catheterization rates of 11,855 patients in a prospective cardiac registry database who underwent single-vessel or multivessel PCI from January 1996 through December 2001. Of this cohort, 11.7% (n = 1,385) had nonsignificant (<50%) LMCAD. Outcomes were compared with those without LMCAD. A secondary analysis was performed on a larger cohort of 34,586 patients undergoing cardiac catheterization, irrespective of mode of revascularization therapy.

RESULTS

Patients with nonsignificant LMCAD had more co-morbidities, and a significantly higher crude mortality rate at 1 year compared with those without LMCAD (4.4% vs. 3.4%; p = 0.05). The 7-year crude mortality hazard ratio (HR) of PCI patients with <50% LMCAD versus those with no LMCAD was 1.18 (95% confidence interval [CI] 0.94 to 1.46). After risk adjustment for differences in baseline clinical profile, however, the HR decreased to 0.98 (95% CI 0.79 to 1.23). Repeat catheterization rates at 1 year did not differ between groups. The secondary analysis in all patients with nonsignificant LMCAD showed an adjusted HR of 1.03 (95% CI 0.94 to 1.14).

CONCLUSIONS

Patients undergoing single-vessel or multivessel PCI who have <50% LMCAD have a nonsignificantly increased 18% relative risk for mortality compared with those without detectable LMCAD that appears to be related to these patients' higher incidence of co-morbidities rather than the left main stenosis itself.

Treatment of Unprotected Left Main Coronary Artery Stenosis in the Drug-Eluting Stent Era

Coronary angiography is often inadequate for estimating the severity of ambiguous left main coronary artery (LMCA) stenoses. Our assessment of these lesions can be improved by the techniques of intravascular ultrasound and fractional flow reserve which provide indices of stenosis severity to enable the prediction of future events and planning of treatment. For patients requiring LMCA revascularization, coronary artery bypass graft (CABG) surgery has been gold standard for decades. However, this technique continues to be limited by factors such as periprocedural mortality, prolonged hospital stay and rehabilitation, and long-term graft patency. LMCA stenosis remains one of the few serious challenges for the interventional cardiologists and, in the bare metal stent era, the long-term results were not sufficient to replace CABG surgery, mainly because of the high restenosis rate. Drug-eluting stents (DES) have dramatically reduced the restenosis rate and early results in small series (approximately 300 patients in total) treated with DES in LMCA have been encouraging, especially for lesions at the ostium and in the left main shaft. Before changes are made in the guidelines for treatment, we must wait for a refinement in the technique and stent design used for bifurcational left main lesion and the results of randomized, specific multicenter studies (SYNTAX trial). It is likely that, for selected patients, LMCA stenosis will be regarded as an indication for PCI.

Intravascular ultrasound-guided treatment for angiographically indeterminate left main coronary artery disease: a long-term follow-up study

OBJECTIVES

The purpose of this study was to evaluate the efficacy of an intravascular ultrasound (IVUS)-guided strategy for patients with angiographically indeterminate left main coronary artery (LMCA) disease.

BACKGROUND

The assessment of LMCA lesions using coronary angiography is often challenging; IVUS provides useful information for assessment of coronary disease.

METHODS

Intravascular ultrasound was performed on 121 patients with angiographically normal LMCAs to determine the lower range of normal minimum lumen area (MLA), defined as the mean - 2 SD. We conducted IVUS studies on 214 patients with angiographically indeterminate LMCA lesions, and deferral of revascularization was recommended when the MLA was larger than this predetermined value.

RESULTS

The lower range of normal LMCA MLA was 7.5 mm(2). Of the patients with angiographically indeterminate LMCAs, 83 (38.8%) had an MLA <7.5 mm(2), and 131 (61.2%) an MLA > or =7.5 mm(2). Left main coronary artery revascularization was performed in 85.5% (71 of 83) of patients with an MLA <7.5 mm(2) and deferred in 86.9% (114 of 131) of patients with an MLA > or =7.5 mm(2). Long-term follow-up (mean 3.3 +/- 2.0 years) showed no significant difference in major adverse cardiac events (target vessel revascularization, acute myocardial infarction, and death) between patients with an MLA <7.5 mm(2) who underwent revascularization and those with an MLA > or =7.5 mm(2) deferred for revascularization (p = 0.28). Based on outcome, the best cut-off MLA by receiver operating characteristic was 9.6 mm(2). Multivariate predictors of cardiac events were age, smoking, and number of non-LMCA vessels diseased.

CONCLUSIONS

Intravascular ultrasound is an accurate method to assess angiographically indeterminate lesions of the LMCA. Furthermore, deferring revascularization for patients with a minimum lumen area > or =7.5 mm(2) appears to be safe.