Personalization of a cardiac electromechanical model using reduced order unscented Kalman filtering from regional volumes.

Patient-specific cardiac modeling can help in understanding pathophysiology and therapy planning. However it requires to combine functional and anatomical data in order to build accurate models and to personalize the model geometry, kinematics, electrophysiology and mechanics. Personalizing the electromechanical coupling from medical images is a challenging task. We use the Bestel-Clément-Sorine (BCS) electromechanical model of the heart, which provides reasonable accuracy with a reasonable number of parameters (14 for each ventricle) compared to the available clinical data at the organ level. We propose a personalization strategy from cine MRI data in two steps. We first estimate global parameters with an automatic calibration algorithm based on the Unscented Transform which allows to initialize the parameters while matching the volume and pressure curves. In a second step we locally personalize the contractilities of all AHA (American Heart Association) zones of the left ventricle using the reduced order unscented Kalman filtering on Regional Volumes. This personalization strategy was validated synthetically and tested successfully on eight healthy and three pathological cases.

Preliminary specificity study of the Bestel-Clément-Sorine electromechanical model of the heart using parameter calibration from medical images.

Patient-specific cardiac modelling can help in understanding pathophysiology and predict therapy effects. This requires the personalization of the geometry, kinematics, electrophysiology and mechanics. We use the Bestel-Clément-Sorine (BCS) electromechanical model of the heart, which provides reasonable accuracy with a reduced parameter number compared to the available clinical data at the organ level. We propose a preliminary specificity study to determine the relevant global parameters able to differentiate the pathological cases from the healthy controls. To this end, a calibration algorithm on global measurements is developed. This calibration method was tested successfully on 6 volunteers and 2 heart failure cases and enabled to tune up to 7 out of the 14 necessary parameters of the BCS model, from the volume and pressure curves. This specificity study confirmed domain-knowledge that the relaxation rate is impaired in post-myocardial infarction heart failure and the myocardial stiffness is increased in dilated cardiomyopathy heart failures.

Is there a Failure to Optimize theRapy in anGina pEcToris (FORGET) study?

BACKGROUND: In the management of chronic stable angina, percutaneous coronary intervention (PCI) provides symptomatic relief of angina rather than improvement of prognosis. Current guidelines recommend optimization of medical therapy prior to elective PCI. It is not clear if these guidelines are adhered to in clinical practice. AIM: The aim of this multi-centre study was to determine the extent to which these treatment guidelines are being implemented in the UK. DESIGN: This was a multi-centre study involving six hospitals in the UK. METHODS: The medical treatment and extent of risk factor modification was recorded for consecutive patients undergoing elective PCI for chronic stable angina at each site. Data collected included anti-anginal drug therapy, lipid levels and blood pressure (BP). Data on heart rate (HR) control were also collected, since this represents a fundamental part of medical anti-anginal therapy. Target HR is <60 b.p.m. for symptomatic angina. RESULTS: A total of 500 patients [74% male; mean age +/- SD (64.4 +/- 10.1 years)] were included. When considering secondary prevention, 85% were receiving a statin and 76% were on an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. In terms of medical anti-ischaemic therapy, 78% were receiving beta-blockers [mean equivalent dose of bisoprolol 3.1 mg (range 1.25-20 mg)], 11% a rate limiting calcium antagonist, 35% a nitrate or nicorandil and one patient was receiving ivabradine. The mean total cholesterol (95% confidence interval) was 4.3 mmol/l (4.2-4.4), mean systolic BP of 130 +/- 24 mmHg and mean diastolic BP of 69 +/- 13 mmHg. Serum cholesterol was <5 mmol/l in 77% and <4 mmol/l in 42% of the patients, 62% of the patients had systolic BP < 140 mmHg and 92% had diastolic BP < 90 mmHg. Considering European Society of Cardiology targets, 50% had systolic BP < 130 mmHg and 76% had diastolic BP < 80 mmHg. A large proportion of patients did not achieve target resting HR; 27% of patients had a resting HR of >or=70 b.p.m., 40% had a resting HR between 60 and 69 b.p.m. and 26% had a resting HR between 50 and 59 b.p.m. The resting HR was not related to the dose of beta-blocker. CONCLUSION: A significant proportion of the patients with chronic stable angina undergoing elective PCI did not achieve therapeutic targets for lipid, BP and HR control. Over 50% of patients did not receive adequate HR lowering anti-anginal therapy to achieve recommended target resting HR.

Comparison of the laminar distribution of input from areas 17 and 18 of the visual cortex to the lateral geniculate nucleus of the cat.

The feedback from area 18 of the cat visual cortex to the lateral geniculate nucleus has been investigated by labeling and reconstructing seventeen axons of known receptive field position and eye preference. The distribution of boutons from each axon was quantified with respect to the compartments of the geniculate complex, and the results were compared with an equivalent analysis of fourteen area 17 axons. Area 18 axons form large, sparse arborizations that extend up to 1.9 mm laterally (1170 +/- 85 microm; mean +/- SEM), with a core of relatively dense innervation spanning on average 600 +/- 70 microm (mean +/- SEM). Thus, they have the potential to influence the transmission of visual information from well beyond their own classical receptive fields. In this respect, they are surprisingly similar to the axons from area 17, despite the fact that the two cortical areas have very different retinotopy. However, there are important differences between the pathways. Area 18 axons project more heavily to the C layers and medial interlaminar nucleus. Whereas the input from both areas to the A layers is biased toward the layer appropriate to the eye preference of each axon, the area 18 input to magnocellular layer C is not. The distribution of area 18 boutons favors the bottom of their preferred A layer, and the area 17 boutons favor the top. These differences mirror those seen in the afferent pathways, suggesting that each cortical area preferentially targets the cells from which it receives input. Finally, their greater diameter suggests that area 18 axons provide the earliest feedback signal in the corticogeniculate loop.

Feedback connections to the lateral geniculate nucleus and cortical response properties.

The cerebral cortex receives sensory input from the periphery by means of thalamic relay nuclei, but the flow of information goes both ways. Each cortical area sends a reciprocal projection back to the thalamus. In the visual system, the synaptic relations that govern the influence of thalamic afferents on orientation selectivity in the cortex have been studied extensively. It now appears that the connectivity of the corticofugal feedback pathway is also fundamentally linked to the orientation preference of the cortical cells involved.