Bi-Modal Arterial Compliance Probe for Calibration-Free Cuffless Blood Pressure Estimation.

OBJECTIVE: We propose a calibration-free method and system for cuffless blood pressure (BP) measurement from superficial arteries. A prototype device with bi-modal probe arrangement was designed and developed to estimate carotid BP - an indicator of central aortic pressure. METHODS: Mathematical models relating BP parameters of an arterial segment to its dimensions and local pulse wave velocity (PWV) are introduced. A bi-modal probe utilizing ultrasound and photoplethysmograph sensors was developed and used to measure diameter values and local PWV from the carotid artery. Carotid BP was estimated using the measured physiological parameters without any subject- or population-specific calibration procedures. The proposed cuffless BP estimation method and system were tested for accuracy, usability, and for potential utility in hypertension screening, on a total of 83 subjects. RESULTS: The prototype device demonstrated its capability of detecting beat-by-beat arterial dimensions and local PWV simultaneously. Carotid diastolic BP (DBP) and systolic BP (SBP) were estimated over multiple cardiac cycles in real-time. The absolute error in carotid DBP was <10 mmHg in 82% cases, and root-mean-square-error = 8.3 mmHg. Consistent with the theory, estimated SBP at the carotid site was lower than the reference brachial SBP. ROC curves obtained for hypertension screening analysis revealed an area under the curve ≥0.8 for both carotid SBP and DBP values, illustrating the potential for using the developed method in hypertension screening. CONCLUSION: The feasibility of calibration-free, cuffless BP measurement at an arterial site of interest was demonstrated with a level of acceptable accuracy. The study also demonstrated the potential utility of the proposed method and system in hypertension screening and local evaluation of arterial stiffness indices. SIGNIFICANCE: Novel approach for calibration-free cuffless BP estimation; a potential tool for local BP measurement and hypertension screening.

Blood Pressure Variability: Assessment, Prognostic Significance and Management.

Interest in blood pressure variability (BPV) as a cardiovascular risk factor has gained focus in recent times. Increased BPV places added strain on the cardiovascular (CV) system unrelated to its average value, leading to increased risk of target organ damage (TOD) and CV events. Recent data suggests that there is inter-drug variation in efficacy with calcium channel blockers (CCBs) such as Amlodipine proving superior to other drugs in reducing BPV. Addition of CCBs to other antihypertensive agents significantly reduces BPV; however the reverse is not true.

Lead aVR--the neglected lead.

The aVR is often neglected lead. It is an unipolar lead facing the right superior surface. As all the depolarisations are going away from lead aVR, all waves are negative in aVR (P, QRS, T) in normal sinus rhythm. In dextrocardia, (True and technical) the p is upright in aVR. The lead aVR is a very important lead in localisation of Coronary Artery Disease. In the presence of anterior ST elevation, ST elevation in lead aVR and V1 denotes proximal LAD obstruction where ST elevation is more in lead V1, than in aVR. In the presence of anterior ST depression, ST elevation in lead aVR indicates Left Main Coronary Artery (LMCA) Disease where ST elevation is more in aVR than in V1. In wide QRS tachycardia, tall R wave in aVR indicates Ventricular Tachycardia rather than SVT with aberrancy. In the presence of QS complexes in inferior leads, the lead aVR helps to differentiate between inferior wall MI (IWMI) and left anterior fascicular block (LAFB). Initial R in aVR is suggestive of IWMI and terminal R is suggestive of LAFB. In pericarditis, lead aVR is most often the only lead which shows reciprocal ST depression where as in Acute Infarction, usually a group of leads shows reciprocal depression. In the presence of persistent ST elevation in anterior chest leads, the R in aVR is suggestive of left ventricular aneurysm (Goldburger's sign). In acute pulmonary embolism, ST elevation in lead aVR is a bad prognostic sign. In Tricyclic antidepressant toxicity, R in aVR more than 3 mm is an adverse prognostic sign. So in variety of conditions, the aVR is proved to be a valuable lead not only in diagnosis but also in predicting the prognosis.

Insulin resistance and coronary artery disease.

A large body of clinical evidence supports aggressive cardiovascular risk management in combination with glycaemic control in patients with type 2 diabetes and insulin resistance. Glycaemic management in a patient with HbA1c that is at or near goal should include an assessment of postprandial glycaemia. Insulin sensitisers have glycaemic and non-glycaemic benefits and warrant consideration even if the HbA1c is not significantly elevated. Oral agents should always be combined with lifestyle modification, including regular exercise and attention to both individual food choices and overall calorie intake to further optimise glycaemic control. For cardiovascular risk reduction, LDL cholesterol as well as HDL cholesterol and triglycerides should be treated appropriately through lifestyle changes. Often pharmacotherapy with at least one lipid-lowering agent is required. Blood pressure control often requires the use of 3 or more antihypertensive agents in patients with diabetes. Clinical data support use of an ACE-inhibitor as first-line therapy for the prevention of micro-albuminuria in patients with diabetes and hypertension. Urine should be tested for micro-albumin at least annually. Low-dose (81 mg) aspirin is appropriate for patients over age 45 years for primary prevention of coronary heart disease. Multifactorial intervention has been shown in large studies such as the Diabetes Prevention Programme and Steno-2 to have significant cardiovascular benefit among patients at risk of developing diabetes and those with type 2 diabetes and micro-albuminuria. Evidence-based treatments and therapeutic goals can build a practical framework for comprehensive outpatient management of patients with type 2 diabetes and insulin resistance. Data from important ongoing studies will continue to shape this framework in the years ahead.