Umair Hayat

Advances in three-dimensional coronary imaging and computational fluid dynamics: is virtual fractional flow reserve more than just a pretty picture?

Percutaneous coronary intervention (PCI) has shown a high success rate in the treatment of coronary artery disease. The decision to perform PCI often relies on the cardiologist’s visual interpretation of coronary lesions during angiography. This has inherent limitations, particularly due to the low resolution and two-dimensional nature of angiography. State-of-the-art modalities such as three-dimensional quantitative coronary angiography, optical coherence tomography and invasive fractional flow reserve (FFR) may improve clinicians’ understanding of both the anatomical and physiological importance of coronary lesions. While invasive FFR is the gold standard technique for assessment of the haemodynamic significance of coronary lesions, recent studies have explored a surrogate for FFR derived solely from three-dimensional reconstruction of the invasive angiogram, and therefore eliminating need for a pressure wire. Utilizing advanced computational fluid dynamics research, this virtual fractional flow reserve (vFFR) has demonstrated reasonable correlation with invasive measurements and remains an intense area of ongoing study. However, at present, several limitations and computational fluid dynamic assumptions may preclude vFFR from widespread clinical use. This review demonstrates the tight integration of advanced three-dimensional imaging techniques and vFFR in assessing coronary artery disease, reviews the advantages and disadvantages of such techniques and attempts to provide a glimpse of how such advances may benefit future clinical decision-making during PCI.

Optical coherence tomography to evaluate coronary stent implantation and complications.

Coronary optical coherence tomography (OCT) is now an established imaging technique in many catheterization laboratories worldwide. With its near-histological view of the vessel wall and lumen interface, it offers unprecedented imaging quality to improve our understanding of the pathophysiology of atherosclerosis, plaque vulnerability, and vascular biology. Not only is OCT used to accurately detect atherosclerotic plaque and optimize stent position, but it can further characterize plaque composition, quantify stent apposition, and assess stent tissue coverage. Given that its resolution of 15 &mgr;m is well above that of angiography and intravascular ultrasound, OCT has become the invasive imaging method of choice to examine the interaction between stents and the vessel wall. This review focuses on the application of OCT to examine coronary stents, the mechanisms of stent complications, and future directions of OCT-guided intervention.

Treatment of hypertension in heart failure with preserved ejection fraction.

Prevalence of Heart Failure with Preserved Ejection (HFPEF) has been rising steadily in the recent past. Studies have shown that at least half of patients presenting with symptoms and signs of heart failure (HF) have preserved left ventricular ejection fraction, i.e. HFPEF, and that this portion of the HF population consists predominantly of women, older age group, and people with hypertension and other cardiovascular risk factors. The morbidity and mortality associated with HFPEF are much higher than the normal population. Chronic hypertension is the most common cause in addition to age, with suggestion of up to 60% of patients with HFPEF being hypertensive. Addressing the specific aetiology and aggressive risk factor modification remain the mainstay in the treatment of HFPEF. Current guidelines recommend the management should involve treatment of hypertension, control of heart rate, venous pressure reduction, and prevention of myocardial ischemia. This review aims to discuss the role of hypertension in the pathophysiology, risk stratification and prognosis of HFPEF, as well as the current available data on various antihypertensive options in this population.

Elevated Blood Viscosity and Microrecirculation Resulting From Coronary Stent Malapposition

One particular complexity of coronary artery is the natural tapering of the vessel with proximal segments having larger caliber and distal tapering as the vessel get smaller. The natural tapering of a coronary artery often leads to proximal incomplete stent apposition (ISA). ISA alters coronary hemodynamics and creates pathological path to develop complications such as in-stent restenosis, and more worryingly, stent thrombosis (ST). By employing state-of-the-art computer-aided design software, generic stent hoops were virtually deployed in an idealized tapered coronary artery with decreasing malapposition distance. Pulsatile blood flow simulations were carried out using computational fluid dynamics (CFD) on these computer-aided design models. CFD results reveal unprecedented details in both spatial and temporal development of microrecirculation environments throughout the cardiac cycle (CC). Arterial tapering also introduces secondary microrecirculation. These primary and secondary microrecirculations provoke significant fluctuations in arterial wall shear stress (WSS). There has been a direct correlation with changes in WSS and the development of atherosclerosis. Further, the presence of these microrecirculations influence strongly on the local levels of blood viscosity in the vicinity of the malapposed stent struts. The observation of secondary microrecirculations and changes in blood rheology is believed to complement the wall (-based) shear stress, perhaps providing additional physical explanations for tissue accumulation near ISA detected from high resolution optical coherence tomography (OCT).

Hourglass appearance on ventriculography: insights from cardiac magnetic resonance imaging.

Clinical introduction A 75-year-old patient with hypertension and severe aortic stenosis underwent elective coronary angiography that showed mild non-obstructive disease in the mid left anterior descending artery (LAD). A left ventriculogram, however, demonstrated segmental systolic dysfunction with dilated akinetic apex (figure 1A, see online supplementary video 1). There was no history of prior myocardial infarction and the patient had not experienced any chest pain recently. A 12-lead ECG showed widespread deep symmetrical inverted T-waves with the exception of leads I, aVL and V1 (see online supplementary figure S1). Cardiac MRI (CMR) was performed to further delineate the morphology of the left ventricle (LV) and a representative frame in late gadolinium phase is shown (figure 1B). Question Above information is most likely consistent with: Takotsubo cardiomyopathy Left ventricular pseudoaneurysm Apical variant of hypertrophic cardiomyopathy (HCM) with aneurysm formation A sequel of prior myocardial infarction in the setting of aortic stenosis Left ventricular non-compaction

Serial three-dimensional optical coherence tomography to assess contained coronary artery perforation.

Introduction Optical coherence tomography (OCT) has gained strong penetrance across catheterization laboratories worldwide. Its exceptional clarity and resolution have seen this modality surpass intravascular ultrasound to assess vulnerable atherosclerotic plaque and contemporary thinstrut coronary stents. Developments in image processing and three-dimensional (3D) reconstructions enable a more detailed understanding of the precise vessel architecture and may help guide percutaneous coronary interventions (PCIs) in a more informed manner. Further, OCT has been used to examine coronary stent complications such as restenosis, thrombosis, and neoatherosclerosis [1]. We present a case where 3D OCT reconstructions provided clear insights into contained coronary perforation following a PCI. A 53-year-old man underwent coronary angiography to evaluate symptoms of angina pectoris. There was a severe stenosis within the proximal-to-mid left anterior descending artery. Following predilatation, a 2.75× 36 mm biolimus-eluting stent (Biomatrix Flex; Biosensors International, Morges, Switzerland) was successfully deployed and postdilated with a 3.0× 9 mm noncompliant balloon to a maximum of 24 atmospheres. Subsequent angiographic imaging showed a small, contrast-filled crater at the mid-segment of the stent (Fig. 1a and b) suggestive of Ellis type-I contained perforation [2]. Throughout the procedure, the patient remained hemodynamically stable, with normal flow.

Optical coherence tomography guiding intervention in acute coronary syndrome.

A 47-year-old man presented with ischaemic chest pain. Initial ECG was normal, but a high-sensitivity troponinT assay was elevated at 724 ng/l (< 15 ng/l). Coronary angiography showed a significant stenosis in the proximal left anterior descending artery with normal TIMI-3 flow (Fig. 1a and b). OCT was performed (iLumien Optis; St Jude Medical, St Paul, Minnesota, USA) at 20 mm/s in the left anterior descending artery during simultaneous flush of iso-osmolar contrast through the guiding catheter. OCT showed a region of poorly reflected light with