Valvular Disease Flashcards
How do you calculate cardiac output?
Answer: cardiac output (CO) = heart rate (HR) x stroke volume (SV)
SV = end diastolic volume (EDV) – end systolic volume (ESV)
Explanation: Cardiac output is the volume of blood the heart pumps in one minute. Frequently given in Litres/minute (but can be also cm3/min)
How do you calculate the ejection fraction?
Answer: ejection fraction (EF) = stroke volume (SV) / end diastolic volume (EDV) x 100
Explanation: Ejection fraction is the volumetric fraction of blood ejected by the ventricle with each contraction. It is commonly given as a percentage (hence multiplication by 100)
How do you calculate mean arterial pressure?
Answer: mean arterial pressure (MAP) = (Cardiac output (CO) x systemic vascular resistance (SVR)) + central venous pressure (CVP)
However at normal resting heart rates MAP can be estimated using systolic and diastolic pressures using the following equation. MAP = Diastolic pressure (DP) + 1/3 (Systolic pressure (SP) – DP). MAP = DP + 1/3(SP-DP).
Explanation: the mean arterial pressure is an average arterial blood pressure throughout a single cardiac cycle of systole and diastole. In health, a MAP >65 mmHg represents the pressure necessary to adequately perfuse the body organs. The estimation of MAP is useable at rest but during exertion (at high heart rate) MAP moves more closely toward an average of SP and DP
Question 4: Calculate MAP, SV, CO and EF for the following case:
A 60 year-old man presented with shortness of breath to A+E. He was in type 2 respiratory failure secondary to an infectious exacerbation of COPD. As a result, he needed intensive care support and had more invasive monitoring. A Swan-Ganz catheter was inserted, which measured end diastolic volume as 142ml and end systolic volume as 47 ml. Observations were that this patient was intubated and ventilated using BiPAP of 20/5 with saturations of 95 percent, heart rate 75 beats per minute, respiratory rate 12/minute, blood pressure 115/75mmHg and Temperature 36.5 degrees Celsius. Work out the mean arterial blood pressure, stroke volume, cardiac output and ejection fraction.
MAP = DP + 1/3 (SP-DP) = 75 + 1/3(115-75) = 88.3 mmHg.
SV = EDV – ESV = 142 – 47 = 95 ml
CO = HR x SV = 75 x 95 = 7125 ml/min or 7.125 L/min
EF = SV/EDV x 100 = 95/142 x 100 = 66.9%
What is infective endocarditis?
Infective endocarditis is an infection of the endocardium or vascular endothelium of the heart
Explanation: ENDO (inner lining), CARD (heart) ITIS (inflammation). Typically affects the heart valves. It is usually the result of bacteria entering the blood stream and forming ”a vegetation” (a bacterial infection surrounded by a layer of platelets and fibrin) in the endocardium. Streptococci (20-40 % of cases) are the most common infection.
How do you diagnose infective endocarditis?
Fever, malaise, sweats and unexplained weight loss are common symptoms
There may be a new heart murmur on examination
Blood tests show anaemia and raised markers of infection
Blood cultures may isolate a microorganism
Echocardiogram can show a vegetation, abscess, valve perforation and/or new dehiscence of prosthetic valve. Often there is regurgitation of the affected valve
Transoesophageal echo has higher sensitivity compared with transthoracic
What features of heart decompensation would you look for?
Answer:
Cardiac decompensation
Symptoms include shortness of breath, frequent coughing, swelling of the legs and abdomen, fatigue
Clinical signs include raised JVP, lung crackles and oedema
Other complications:
Vascular and embolic phenomena
(stroke, Janeway lesions, splinter/ conjunctival haemorrhages)
Immunological phenomena
(Osler’s nodes, Roth spots)
What features of heart decompensation would you look for?
Answer:
Cardiac decompensation
Symptoms include shortness of breath, frequent coughing, swelling of the legs and abdomen, fatigue
Clinical signs include raised JVP, lung crackles and oedema
Other complications:
Vascular and embolic phenomena
(stroke, Janeway lesions, splinter/ conjunctival haemorrhages)
Immunological phenomena
(Osler’s nodes, Roth spots)
What part of the heart does infective endocarditis affect?
Answer:
Infective endocarditis affects the endocardium, especially the valves of the heart
Aortic valve is affected most frequently (aortic > mitral > right-sided valves)
Explanation: The formation of a vegetation at the valves of the heart either results in changes to their thickness or a failure in their ability open and close appropriates. It is more common for bacteria to attach to the endocardium if underlying damage is present, and this occurs more frequently at sites of turbulent blood flow such as the valves of the heart.
How might this vary for intravenous drug users?
Answer: Intravenous drug users are at increased risk of infective endocarditis due to repeated injection – potentially exposing their bloodstream to bacteria on the surface of the skin or use of non-sterile needles.
Explanation: Entry of bacteria into the blood stream is first and critical step in infective endocarditis. Increased risk of infective endocarditis is therefore seen in I.V. drug users, but also a complication of routine surgeries such as dental surgery. It is also more common in individuals that are immunosuppressed or have congenital heart defects leading to damaged endocardium.
What is the definition of dilated cardiomyopathy?
Answer: dilated cardiomyopathy is characterised by dilated and thin-walled cardiac chambers with reduced contractility
Explanation: Dilation of the chambers leads to reduced contractility. Echo shows a dilated left ventricle with reduced systolic function (ejection fraction) and typically global hypokinesis
What are the commonest causes of dilated cardiomyopathy?
Answer: Idiopathic, genetic, toxins (alcohol, cardiotoxic chemotherapy), pregnancy (peripartum cardiomyopathy), viral infections (myocarditis), tachycardia-related cardiomyopathy, thyroid disease, muscular dystrophies
How is the condition managed?
Answer:
Medical heart failure therapy - ACE inhibitors, beta-blockers, mineralocorticoid receptor antagonists
Diuretics for fluid overload
Anticoagulation for atrial fibrillation
Cardiac devices – cardiac resynchronisation therapy and/or implantable cardioverter defibrillator
Transplant
What will be the implications on this gentleman in the future?
Answer: The gentleman is at risk of heart failure hospitalization, cardiac arrhythmias, sudden cardiac death due to ventricular arrhythmia, and reduced survival
