Percutaneous coronary intervention

PCI consists of balloon angioplasty followed by stenting.

Balloon angioplasty expands the coronary lumen by stretching and tearing the atherosclerotic plaque and vessel wall. The atherosclerotic plaque is also redistributed a little along its longitudinal axis. Elastic recoil of the stretched vessel wall generally leaves a 30 to 35 percent residual diameter stenosis. Although stand-alone balloon angioplasty is rarely used other than for very small (<2.25 mm) vessels, balloon angioplasty remains integral to PCI for predilating lesions before stent placement, deploying coronary stents, and further expanding stents after deployment.

Coronary stents are currently used in more than 90 percent of PCI procedures worldwide. Coronary stents lowers the incidence of vessel closure. Restenosis after coronary stent placement occurs in some patients due to excessive intimal hyperplasia within the stent.

While bare metal coronary stents reduce the incidence of angiographic and clinical restenosis compared to balloon angioplasty, angiographic restenosis (follow-up diameter stenosis >50 percent) still occurs in 20 to 30% of patients and clinical restenosis (recurrent angina due to restenosis in the treated segment) develops in 10 to 15 percent of patients in the first year after treatment. Restenosis with bare metal coronary stents occurs more often in patients with small vessels, long lesions, and in patients with diabetes mellitus. Use of drugs has not prevented restenosis after stent placement.

Drug-eluting stents, on the other hand, provide sustained local delivery of an anti-proliferative agent at the site of vessel wall injury. Trials have demonstrated the benefit of drug-eluting stents in patients with long (>20 mm length) and small (<2.5 mm) vessels. This type of stent placement requires extended (up to 1 year) therapy with the combination of aspirin and clopidogrel to prevent stent thrombosis.

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Hypokalemia - Potassium replacement calculation

DEFINITION Hypokalemia is defined as a serum potassium level of less than 3.5 mmol/L. Normal level= 3.5-5.5 mmol/L. It is encountered in >20% of patients. Patients are usually asymptomatic but severe arrhythmias and rhabdomyolysis can occur. Non-specific complaints include easy fatiguability and skeletal muscle weakness. The preferred method of replacement is via the oral route but at times this is not possible. The article below will give you an idea about how to calculate the amount of KCl to be given I.V. 1) Potassium deficit in mmol is calculated as given below: K deficit (mmol) = (K normal lower limit - K measured ) x kg body weight x 0.4 2) Daily potassium requirement is around 1 mmol/Kg body weight. 3) 13.4 mmol of potassium found in 1 g KCl . ( molecular weight KCl = 39.1 + 35.5 = 74.6) Suppose we get an asymptomatic patient of 70 Kg with a serum potassium level of 3.0 mmol/L and he is on nil by mouth but having...

Endomysium, Perimysium and epimysium - definition, histology

Each muscle fibre is closely surrounded by connective tissue. This acts as a support for the muscle fibres and unites them to each other. 1) Each muscle fibres is surrounded by delicate connective tissue that is called the endomysium . 2) Individual fasciculi are enclosed by a stronger sheath of connective tissue called the perimysium . 3) The entire muscle is surrounded by connective tissue called the epimysium . This is illustrated by the schematic diagram below. 1= perimysium, 2= endomysium, 3= fasciculus. At the junction of a muscle with a tendon, the fibres of the endomysium, the perimysium and the epimysium become continuous with the fibres of the tendon. First published on: 27 December 2016

The plantar reflex - Babinski's sign

The plantar response is an important test to identify an upper motor neuron lesion. PROCEDURE To elicit it, the muscles of the lower limbs must be relaxed. The outer edge of the sole of the foot is stimulated by firmly scratching a blunt object like a key or a stick along it from the heel towards the little toe. This is what Joseph Babinski did in the year 1896. He described the 'great toe sign' that year and then in 1903 the 'toe abduction or fan sign'. Nowadays, a final medial movement across the sole of the metatarsus is also done. i.e. we start at the heel to the little toe and finally arcing to the big toe. The final arcing movement is absent in the original Babinski plantar response test. Babinski sign refers to a combination of 'the great toe sign' and the 'fan sign'. SIGNIFICANCE The normal response is plantar flexion of the toes (down going) and they are drawn together. More precisely, there is flexion of the big toe and addu...

Differences between hyperemia and congestion

Hyperemia and congestion both indicate a local increased volume of blood in a particular tissue. Hyperemia is an active process that result from augmented blood flow due to arteriolar dilation (e.g. at sites of inflammation or in skeletal muscle during exercise). The affected tissue is redder than normal because of engorgement with oxygenated blood. Congestion, on the other hand, is a passive process resulting from impaired venous return out of a tissue. It may occur due to systemic causes like cardiac failure or a local cause like isolated venous obstruction. The tissue is cyanosed because the worsening congestion leads to accumulation of deoxygenated hemoglobin in the affected tissues.

Apgar scoring - table, mnemonic

INTRODUCTION The Apgar score was devised in 1952 by Dr Virginia Apgar (anesthesiologist) as a simple and repeatable method to quickly and summarily assess the health of newborn children immediately after birth. This helps to identify those requiring resuscitation and can also be used to predict survival in the neonatal period. MNEMONIC A mnemonic for learning purposes includes: A - Appearance (skin colour) P - Pulse (heart rate) G - Grimace (reflex irritability) A - Activity (muscle tone) R - Respiration Another mnemonic is also useful: How - Heart rate Ready - Respiration Is - Irritability This - Tone Child - Colour Apgar scoring is divided into 1 and 5-min scores. 1-MIN SCORE Sixty seconds after complete birth, the five parameters specified in the table above must be eval...

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