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

Intravascular imaging for left main stem assessment: An update on the most recent clinical data

Left main (LM) stem has different structural and anatomical characteristics compared to all of the other segments of the coronary tree, thus its management through percutaneous coronary intervention (PCI) is a challenge and is associated with worse clinical outcome and higher need for revascularization as compared to other lesion settings. Intravascular imaging, by means of intravascular ultrasound (IVUS) or optical coherence tomography (OCT), is an important tool for LM PCI guidance, aiming at improving the immediate performance and the long term outcome of this procedure. Following current guidelines and recent scientific findings, IVUS becomes important to firstly assess, and finally evaluate the result of LM stenting, according to the experience and preferences of the operator. The role of OCT still remains to be defined, but recent data is shedding light also on this imaging technique. The aim of this review is to highlight the latest scientific advancements regarding intravascular imaging in LM coronary artery disease.

Sodium-glucose Cotransporter Type 2 Inhibitors: A New Insight into the Molecular Mechanisms of Diabetic Nephropathy

Diabetic nephropathy is one of the chronic microvascular complications of diabetes and is a leading cause of end-stage renal disease. Fortunately, clinical trials have demonstrated that sodium-glucose cotransporter type 2 inhibitors could decrease proteinuria and improve renal endpoints and are promising agents for the treatment of diabetic nephropathy. The renoprotective effects of sodium-glucose cotransporter type 2 inhibitors cannot be simply attributed to their advantages in aspects of metabolic benefits, such as glycemic control, lowering blood pressure, and control of serum uric acid, or improving hemodynamics associated with decreased glomerular filtration pressure. Some preclinical evidence suggests that sodium-glucose cotransporter type 2 inhibitors exert their renoprotective effects by multiple mechanisms, including attenuation of oxidative and endoplasmic reticulum stresses, anti-fibrosis and anti-inflammation, protection of podocytes, suppression of megalin function, improvement of renal hypoxia, restored mitochondrial dysfunction and autophagy, as well as inhibition of sodium-hydrogen exchanger 3. In the present study, the detailed molecular mechanisms of sodium-glucose cotransporter type 2 inhibitors with the actions of diabetic nephropathy were reviewed, with the purpose of providing the basis for drug selection for the treatment of diabetic nephropathy.

Mechanisms of action of SGLT2 inhibitors and their beneficial effects on the cardiorenal axis

Large clinical studies conducted with sodium-glucose co-transporter 2 inhibitors (SGLT2i) in patients with type 2 diabetes and heart failure with reduced ejection fraction have demonstrated their ability to achieve both cardiac and kidney benefits. Although there is huge evidence on SGLT2i-mediated clinical benefits both in diabetic and non-diabetic patients, the pathophysiological mechanisms underlying their efficacy are still poorly understood. Some favorable mechanisms are likely due to the prompt glycosuric action which is associated with natriuretic effects leading to hemodynamic benefits as well as a reduction in glomerular hyperfiltration and renin-angiotensin-aldosterone system activation. In addition to the renal mechanisms, SGLT2i may play a relevant role in cardiorenal axis protection by improving the cardiomyocyte metabolism, by exerting anti-fibrotic and anti-inflammatory actions, and by increasing cardioprotective adipokine expression. New studies will be needed to better understand the specific molecular mechanisms that mediate the SGLT2i favorable effects in patients suffering diabetes. Our aim is to first discuss about the molecular mechanisms underlying the cardiovascular benefits of SGLT2i in each of the main organs involved in the cardiorenal axis. Furthermore, we update on the most recent clinical trials evaluating the beneficial effects of SGLT2i in treatment of both diabetic and non-diabetic patients suffering heart failure.

Physiology-Based Revascularization of Left Main Coronary Artery Disease

It is of critical importance to correctly assess the significance of a left main lesion. Underestimation of significance beholds the risk of inappropriate deferral of revascularization, whereas overestimation may trigger major but unnecessary interventions. This article addresses the invasive physiological assessment of left main disease and its role in deciding upon revascularization. It mainly focuses on the available evidence for fractional flow reserve and instantaneous wave-free ratio, their interpretation, and limitations. We also discuss alternative invasive physiological indices and imaging, as well as the link between physiology, ischemia, and prognosis.

Hybrid coronary revascularization versus total arterial revascularization for the treatment of left main coronary artery disease

Background

Hybrid coronary revascularization (HCR) has a similar clinical outcome to coronary artery bypass grafting (CABG) in treating multivessel disease. However, the outcome of HCR in treating left main coronary artery (LM) disease is unclear. This study sought to compare the clinical outcome of HCR with total arterial revascularization (TAR) for treating LM disease.

Methods

Patients who underwent treatment for LM disease in our center between January 2009 and December 2019 were selected. Of these, 33 patients underwent HCR, and 70 patients underwent TAR. The primary efficacy outcome of this study was mid-term major adverse cardiac and cerebrovascular events (MACCE). The primary safety outcome was perioperative MACCE.

Results

The incidence of postoperative outcomes was comparable between the two groups after adjustment with inverse probability weighting (IPW) (P>0.05). The median follow-up time was 47 (interquartile range, 20 to 85) months. There was no significant difference in the incidence of all mid-term outcomes and the freedom of MACCE between the two groups after adjustment (P>0.05). The Cox proportional hazard model demonstrated that HCR was not a significant determinant for MACCE [hazard ratio (HR) =3.516, 95% confidence interval (CI): 0.835 to 14.813].

Conclusions

HCR may be safe and effective for the treatment of LM disease compared with TAR.

Sodium-glucose cotransporter type 2 inhibitors for the treatment of type 2 diabetes mellitus

The management of type 2 diabetes mellitus (T2DM) is becoming increasingly complex. Sodium-glucose cotransporter type 2 inhibitors (SGLT2is) are the newest antidiabetic agents for T2DM. By targeting the kidney, they have a unique mechanism of action, which results in enhanced glucosuria, osmotic diuresis and natriuresis, thereby improving glucose control with a limited risk of hypoglycaemia and exerting additional positive effects such as weight loss and the lowering of blood pressure. Several outcome studies with canagliflozin, dapagliflozin or empagliflozin reported a statistically significant reduction in major cardiovascular events, hospitalization for heart failure and progression to advanced renal disease in patients with T2DM who have established atherosclerotic cardiovascular disease, several cardiovascular risk factors, albuminuric mild to moderate chronic kidney disease or heart failure. Current guidelines proposed a new paradigm in the management of T2DM, with a preferential place for SGLT2is, after metformin, in patients with atherosclerotic cardiovascular disease, heart failure and progressive kidney disease. Ongoing trials might extend the therapeutic potential of SGLT2is in patients with, but also without, T2DM. This Review provides an update of the current knowledge on SGLT2is, moving from their use as glucose-lowering medications to their new positioning as cardiovascular and renal protective agents.

Effects of Sodium-Glucose Co-transporter 2 Inhibition with Empaglifozin on Renal Structure and Function in Non-diabetic Rats with Left Ventricular Dysfunction After Myocardial Infarction

Background

The use of sodium–glucose co-transporter 2 inhibitors (SGLT2i) is currently expanding to cardiovascular risk reduction in non-diabetic subjects, but renal (side-)effects are less well studied in this setting.

Methods

Male non-diabetic Sprague Dawley rats underwent permanent coronary artery ligation to induce MI, or sham surgery. Rats received chow containing empagliflozin (EMPA) (30 mg/kg/day) or control chow. Renal function and electrolyte balance were measured in metabolic cages. Histological and molecular markers of kidney injury, parameters of phosphate homeostasis and bone resorption were also assessed.

Results

EMPA resulted in a twofold increase in diuresis, without evidence for plasma volume contraction or impediments in renal function in both sham and MI animals. EMPA increased plasma magnesium levels, while the levels of glucose and other major electrolytes were comparable among the groups. Urinary protein excretion was similar in all treatment groups and no histomorphological alterations were identified in the kidney. Accordingly, molecular markers for cellular injury, fibrosis, inflammation and oxidative stress in renal tissue were comparable between groups. EMPA resulted in a slight increase in circulating phosphate and PTH levels without activating FGF23–Klotho axis in the kidney and bone mineral resorption, measured with CTX-1, was not increased.

Conclusions

EMPA exerts profound diuretic effects without compromising renal structure and function or causing significant electrolyte imbalance in a non-diabetic setting. The slight increase in circulating phosphate and PTH after EMPA treatment was not associated with evidence for increased bone mineral resorption suggesting that EMPA does not affect bone health.

Electronic supplementary material

The online version of this article (10.1007/s10557-020-06954-6) contains supplementary material, which is available to authorized users.

Left main coronary artery disease: pathophysiology, diagnosis, and treatment

The advent of coronary angiography in the 1960s allowed for the risk stratification of patients with stable angina. Patients with unprotected left main coronary artery disease have an increased risk of death related to the large amount of myocardium supplied by this vessel. Although coronary angiography remains the preferred imaging modality for the evaluation of left main coronary artery stenosis, this technique has important limitations. Angiograms of the left main coronary artery segment can be difficult to interpret, and almost one-third of patients can be misclassified when fractional flow reserve is used as the reference. In patients with clinically significant unprotected left main coronary artery disease, surgical revascularization was shown to improve survival compared with medical therapy and has been regarded as the treatment of choice for unprotected left main coronary artery disease. Two large-scale clinical trials published in 2016 support the usefulness of catheter-based revascularization in selected patients with unprotected left main coronary artery disease. In this Review, we describe the pathophysiology of unprotected left main coronary artery disease, discuss diagnostic approaches in light of new noninvasive and invasive imaging techniques, and detail risk stratification models to aid the Heart Team in the decision-making process for determining the best revascularization strategy for these patients.

Renal effects of sodium-glucose cotransporter-2 inhibitors in patients with type 2 diabetes and renal impairment

In patients with type 2 diabetes (T2D), microvascular changes in the kidney often result in diabetic kidney disease (DKD), the progression of which is associated with an increased risk of cardiovascular (CV) and all-cause mortality. Sodium-glucose cotransporter-2 inhibitors (SGLT-2is) are a newer class of oral glucose-lowering therapies that were associated with significant reductions in the risk of major adverse CV events, CV death, and hospitalization for heart failure compared with placebo in CV outcomes trials (CVOTs) of patients with T2D and established CV disease or varying levels of CV risk. In addition, SGLT-2is reduced the risks of clinically relevant renal outcomes in these large randomized studies, indicating the potential for renoprotective effects in patients with T2D and DKD. This review discussed the non-glycemic effects of SGLT-2is in patients with T2D and renal impairment, including reductions in systolic and diastolic blood pressure, decreases in albuminuria and plasma uric acid, changes in estimated glomerular filtration rate, and minimal changes in electrolytes. Potential mechanisms for the renoprotective effects of SGLT-2is observed in CVOTs were considered, including the likely incremental benefits of SGLT-2is when added to renin-aldosterone-angiotensin system inhibitors (RAASis). The possibility of extending the use of SGLT-2is to patients with non-DKD was also discussed. Although the exact mechanisms by which SGLT-2is improve renal outcomes are not fully understood, they are likely to be multifactorial and additive when these drugs are used in combination with RAASis in patients with DKD.

Percutaneous or surgical revascularization for left main stem disease: NOBLE ideas, but do they EXCEL?

Introduction: Although coronary artery bypass grafting (CABG) has traditionally been the standard treatment for significant left main stem (LMS) disease, percutaneous coronary intervention (PCI) using drug-eluting stents (DES) is now considered an acceptable alternative. Areas covered: This article aims to summarise the key findings of the landmark clinical trials on LMS revascularization and the recently published ESC/EACTS guidelines on myocardial revascularization related to LMS disease. Expert opinion: It is unlikely that there will be a further large randomized trial aimed at addressing the issue of the optimum method of revascularization for LMS disease. Both PCI and CABG are reasonable revascularization options for appropriately selected patients with LMS disease. 'Heart Team' approach is vital to guide the management of patients with LMS disease, when there is obvious clinical equipoise and a mandate for complete revascularization. With an aging and increasing co-morbid patient population, clinical equipoise may not always be obvious, making extrapolation of clinical trial results to the 'real world' difficult.

Technical Considerations in Transradial Unprotected Left Main Stem Rotational Atherectomy-Assisted and IVUS-Guided Percutaneous Coronary Intervention Using the 7.5F Eaucath Sheathless Guiding Catheter System

Rotational atherectomy-assisted percutaneous coronary intervention (PCI) on unprotected left main stem (LMS) bifurcation lesions is technically challenging. Intravascular ultrasound (IVUS) has become a standard part of the PCI procedure for the treatment of LMS disease. There is limited experience in performing these cases via a transradial approach using a sheathless guiding catheter (SGC) system. We report a case of a symptomatic octogenarian patient with restrictive angina and significant LMS bifurcation disease, who was successfully treated transradially with the use of the 7.5F Eaucath SGC system and we describe the technical challenges encountered with this strategy.