Glossary Of Terms - V

Vaccine Vagus nerve under collapse Valve Valve surgery Valvuloplasty Variable
Vascular Vasodilators Vasovagal fainting under collapse Vein Vena cava Ventricle
Vitamins VO2 max, fitness

Vaccine is a substance to cause active immunity against a specific infectious disease.

Vagus nerve see vagus nerve under collapse.

Valency. See valency under Organic chemistry.

Valsartan. See valsartan under Angiotensin converting enzyme inhibitors.

Valve. A human heart has four valves, two on the right and two on the left.

The two on the right side of the heart are the tricuspid valve between the right atrium and the right ventricle; and pulmonary valve between the right ventricle and the pulmonary artery from there to the lungs. These two valves govern the flow of blood through the heart to the lungs. In adults it is rare for these valves to need operations.

The two valves on the left side of the heart are the mitral valve, between the left atrium and the left ventricle; and aortic valve between the left ventricle and the aorta. These govern the flow of blood through the heart and out to the rest of the body. Usually these are the two valves that become narrow or restricted – called stenosed, or start to leak significantly – regurgitation, and that may need to be repaired or replaced.

Valve surgery. If your cardiologist has established that your symptoms of breathlessness, chest pain, dizziness or faintness are due to a malfunctioning heart valve, you may need an operation to repair or replace the affected valve or valves. After the operation you will notice a significant improvement in your symptoms. Valve surgery may also reduce or prevent changes associated with long-term heart muscle strain.

See separate factsheet on Valve Surgery and Valvuloplasty.

Valvuloplasty involves inflating a balloon inside a valve to widen it. Compare Balloon angioplasty. Valvuloplasty is a painless procedure and is carried out under local anaesthetic. You may have to stay in hospital about three or four days.

See separate factsheet on Valve Surgery and Valvuloplasty.

Variable has several meanings. A variable is something that can be observed, measured or calculated for every patient in a selected group. It may also apply to a quantity that has a range of possible values. Variable can also mean liable to change. It may also apply to something liable to vary from the established type or pattern. It also applies to something that can be varied but in a controlled way.

An independent variable in an equation or assertion is a variable or argument that is free to take any valid value. In maths it is often denoted by x. Extending this idea, any patient identifier – such as hospital number – can be regarded as an independent variable, since for a particular value of that identifier there will be observed values of other variables.

A dependent variable, denoted typically by y, is one that can be calculated from – or is related through equations to – the independent one. By extension, something that has an observed value for each patient can be treated like a dependent variable.

Vascular means relating to or having vessels that circulate fluids.

Vascular disease means disease of the blood vessels – the cause of heart attacks, most strokes, angina, and other related conditions. See Cardiovascular.

Vasodilators are drugs that widen blood vessels – arteries and veins. They are particularly used to reverse the narrowing of arteries or veins where this is causing reduced blood flow, which reduces the amount of oxygen available to that part of the body. This occurs in angina.
Vasodilators are also used to treat hypertension = high blood pressure. Widening the arteries reduces the strain on the heart and helps to reduce blood pressure. Vasodilators and calcium channel blockers act on the muscles of the walls of arteries to prevent narrowing. See Antihypertensive.

Vein. A vein is a blood vessel in which blood flows towards the heart from part of the rest of the body.

Vena cava. A vena cava is either one of the two large veins that carry low-oxygen blood back to the heart. They are the inferior vena cava, IVC, and the superior vena cava, SVC.

Venous distension means swollen veins, eg of the neck. See HF diagnosis.

Venogram. A venogram is an X-ray of the leg veins to observe blood clots, usually with a trace of a dye that shows up on the X-ray. It helps diagnosis of deep vein thrombosis.

Ventral means towards or relating to the front of the body or towards the belly. Opposite of dorsal. Also see Anterior.

Ventricle. The right ventricle RV is the lower-right chamber of the heart. Similarly the left ventricle LV is the lower-left chamber. Blood is pumped from the left ventricle to the rest of the body along arteries, and from the right ventricle to the lungs. LVEF = Left ventricular ejection fraction - see Ejection fraction.

Ventricular fibrillation is an irregular twitching of the heart muscle wall, interfering with the normal rhythm of the ventricles. The electrical impulses may become chaotic, so the heart muscles do not respond correctly. It is often corrected by early use of a defibrillator. See Cardiac arrest, Automatic external defibrillator, and Supraventricular tachycardia.

Ventricular septal defect, VSD is a defect of the wall between the two ventricles of the heart. It is a hole between the left and right ventricles. So blood can pass between these, and mainly flows from the left ventricle to the right ventricle. Thus excess blood recirculates through the lungs. Large holes can flood and/or damage the lungs. However, small holes cause few problems. About 15% of babies are born with such small holes and these usually close up without treatment. See septal.

Verapamil is a calcium channel blocker.

Viscosity. Viscosity is a measure of the extent to which a liquid such as blood does not flow easily – its stickiness. Eg syrup or treacle is more viscous than water. See International Normalized Ratio.

Vitamins are natural substances that are essential for life, health growth and metabolism.

Generally, processed and overcooked foods have less vitamins than fresh, raw, or lightly cooked foods.

Under diet it is suggested that people cannot correctly absorb and/or process some vitamins unless certain proteins and/or other vitamins are already present, eg from oily fish, poultry and other foods.

Insufficient supply of a particular vitamin typically results in a deficiency disease. The usual minimum daily requirements are based on the Reference Nutrient Intake. People with deficiency of a vitamin may need higher quantities, as can be determined by a doctor.

People should not normally* take more than the recommended quantity of each – particularly of fat-soluble vitamins that may accumulate in the body. *Here 'normally' means that patients severely deficient in a particular vitamin will need more and be under medical supervision. Overdose does not help and may cause serious harm.

Most people may take supplementary vitamin tablets without risk, but should not need such.

Vitamins are any of a group of compounds that are essential in small quantities for the body's normal metabolism. They cannot be synthesized in the body, but they occur naturally in various foods.

Under diet it is suggested that people cannot correctly absorb and/or process some vitamins unless certain proteins and/or other vitamins are already present, eg from oily fish, poultry and other foods.

Insufficient supply of a particular vitamin typically results in a deficiency disease. The usual minimum daily requirements are based on the Reference Nutrient Intake. People with deficiency of a vitamin may need higher quantities, as can be determined by a doctor.

The following table summarizes the main vitamins, why needed, and food sources. Different sources of such information give slightly differing foods for some vitamins. In the table * means not as good a source as ● and in some cases the best sources are given in words.

VitaminOily fishPoultryRed meatLiver/
EggsCerealsGreen vegRoot vegPulsesNutsFruit
A; protect skin & internal tissues, acne, night vision; in ●carrots, halibut oil   ** *  
folic acid; neural defects, anaemia          
B1 thiamine; metabolism; in ●rice         
B2 riboflavin; metabolism*     
B3 niacin; lipid-lowering, reduce LDL, convert food into energy        
B5 pantothenic acid; cell growth           
VitaminOily fishPoultryRed meatLiver/ kidneyMilkCheeseButter/ margEggsCerealsGreen vegRoot vegPulsesNutsFruit
B6 pyridoxine; metabolism catalyst        
B12 cyanocobalamin; carry oxygen        
C ascorbic acid; anaemia; ●citrus fruit, tomatoes, green veg, see below         *  
D calciferol; bone disorders, rickets            
E tocopherol; reproduction, antioxidant        
H biotin; dermatitis, hair          
K prothrombin; blood plasma clotting         *   
P; regulates flow in capillaries; ● citrus fruit, blackcurrants, rose hip             

Vitamin B3, niacin, cannot be stored in the human body, so people need some every day - typically 17mg for men and 13mg for women. These amounts are in two average-size chicken breasts for example. It also raises the level of HDL and reduces the level of LDL. It may also dilate (expand) blood vessels. It triggers the release of prostaglandin 2, which helps the endothelium, the lining of a blood vessel, to relax and thus let more blood flow.

Vitamin C is present in fruits and vegetables. It prevents scurvy, which shows as anaemia, spongy gums, and bleeding from beneath the skin. In infants shortage of Vitamin C causes badly formed teeth and bones. Vitamin C helps prevent anaemia when taken with iron-rich foods such as pure orange juice, meat, fish, eggs, and pulses.

Research has shown that people with high levels of Vitamin C in their blood live on average six years longer than others with low Vitamin C. But this may partly be due to other factors such as lifestyle, environment and wealth. Those eating a low-GI diet had increased levels of Vitamin C absorbed from their foods – see under High GI.

Voluntary eg voluntary movements - see under nerve. Involuntary means carried out without any conscious wish to do whatever; or unintentional.

Volume of oxygen. See Fitness from volume of oxygen and VO2 max.

VSD = Ventricular septal defect - a defect of the wall between the two ventricles of the heart.


This information was created and edited by Richard Maddison for the BCPA.
Copyright © 1997-2019 The British Cardiac Patients Association, and/or Richard Maddison.
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First published in this form 2002, and updated 2005, 2007, 2008, 2011, 2012, 2013, 2017.
All rights reserved. No part of this work may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, without written permission from the BCPA Head Office.

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Authors, sources and acknowledgements

The main sources are BCPA Journal published articles, other information from authors, and publicly available documents and websites. In many cases the journal articles give sources and further information than the Glossary entries.

Parts of the wordings under ECG and Echocardiogram are adapted with permission from BUPA's health information resources, available at

We hope we have thanked everyone.

Richard Maddison

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