Case 4: Acute-on-chronic Breathlessness Flashcards
A Wave (Cardiac Cycle)
end diastole
V Wave (Cardiac Cycle)
late systole
V Wave (Cardiac Cycle)
early systole
diastole
relaxation of heart
systole
contraction of heart
p wave
atrial depolarisation
QRS complex
ventricular depolarisation and atrial repolarisation
t wave
ventricular repolarisation
Symptoms of heart failure
Tachycardia, decreased exercise tolerance, dyspnea, peripheral and pulmonary edema, cardiomegaly
Heart failure is the most likely cause due to the combination presence of dyspnoea, oedema, elevated JVP, basal crepitations.
Dyspnoea
by definition refers to a state where the subject is uncomfortably aware of his/her breathing. It is usually associated with either the increase in the work of breathing - associated with reduced lung compliance (stiff lungs) or increased respiratory rate. It is therefore a non-specific symptom and may occur in diseases pertaining to the cardiovascular, respiratory systems or in the presence of severe anaemia. Review the causes of dyspnoea in these systems.
diaphoretic
sweating
Furosemide
loop diuretic used in the treatment of congestive heart failure and oedema
Loop diuretics MOA
Act on ascending loop of Henle, inhibit sodium-potassium-chloride transporter; decrease renal vascular resistance
investigations for presentation of heart failure
BNP
FBC
ECG
LFT
CXR
ABG
action potential in the heart starts in the
sinoatrial node
rapid depolarization
massive influx of sodium ions
voltage dependant inactivation
The fast inactivation of voltage-dependent calcium channels is an important, intrinsic regulatory mechanism that helps to precisely control the amount of calcium entering excitable cells during membrane depolarizations.
His-Purkinje system
portion of the conduction system consisting of the bundle of His, bundle branches, and Purkinje fibers
pacemaker
A group of cells located in the right atrium that sends out signals that make the heart muscle contract and that regulates heart rate.
myogenic mechanism
based on the tendency of smooth muscle to contract when stretched
Abnormal Pacemaker Function
bradycardia
tachycardia
ectopic pacemaker
Triggered arrhythmias
Early afterdepolarizations (torsades de pointes) occur in phase 2 or 3, before cell has repolarized
Treat by shortening AP, or decrease dose of antiarrhythmic patient is already on
Delayed afterdepolarizations occur in phase 4, after cell has repolarized but before normal successive depolarization would occur
Treat by reducing Ca overload, decreasing digitalis dose
Early After Depolarization Causes
Decreased outward K current > prolonged APD
Can be genetic or acquired - problem with drug potential
APD
cardiac action potential duration
cellular calcium overload
heart failure
spontaneous ca release from SR
activates depolarising membrane currents
Reentrant arrhythmias
Arrhythmias of abnormal conduction; they involve the repetitive movement of an impulse through
tissue previously excited by the same impulse
might be due to an area of dead heart
- unidirectional block
unidirectional block
a type of partial conduction block in which impulses travel in one direction but not in the opposite one
might be a mismatched refractory period
post infarction
excitation-contraction coupling
events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract
Lusitropic
affects cardiac relaxation
Lusitropic effect
more rapid relaxation (after contraction)
caused by catecholamines
catecholamines effect on heart
^ L type ca current - more trigger and loading
^ SERCA via phosphorylation of phospholamban
SERCA
Sarcoplasmic Endoplasmic Reticulum Calcium ATPase
L-type calcium channels
Slow, long acting channels that open during cardiac depolarization
T-type calcium channels
Fast, transient channels that are open during phase 0 and help create the depolarization upstroke of the myocyte action potential
Phospholamban
regulatory protein in contractile myocardium that alters Ca2+ ATPase activity in the sarcoplasmic reticulum
orthopnea
ability to breathe only in an upright position
Orthopnoea is the sensation of breathlessness that occurs when lying flat causing the person to have to sleep propped up in bed or sitting in a chair. It is often a symptom of left ventricular failure and/or pulmonary oedema but is also experienced by patients with chronic respiratory disorders.
Orthopnea in heart failure
In heart failure, orthopnoea occurs because on lying flat, there is increased venous return to the heart from the lower extremities of the body. This results in increased blood flow to the pulmonary circulation. In normal physiology, the left ventricular stroke volume will increase to compensate. However, in heart failure, the weakened heart isn’t strong enough to pump out this extra volume, leading to pooling of blood in the pulmonary circulation. Elevated intravascular pressure in the pulmonary circulation results in fluid leakage into the alveoli, and therefore pulmonary oedema.
JVP (jugular venous pressure)
reflects the volume & pressure of venous blood in the right side of the heart
Kussmaul sign= JVP increases during inhalation
How do you differentiate between the jugular vein and the carotid pulse in the neck?
The jugular vein sits in between the two heads of the sternocleidomastoid muscle and the earlobe. It is not visible unless it is elevated or unless pressure is placed on the liver (called the hepatojugular reflex). The carotid artery lies just medial to the internal jugular vein and is palpated at the point of the C wave, (see below) which occurs between the A and V waves of the JVP. The carotid pulsation does not alter when pressing on the liver. Unlike the carotid pulse which has one pulsatile wave, the JVP has three waves
hepatojugular reflex
Sustained elevated jugular venous pressure that occurs during abdominal compression; indicates that hepatic venous congestion is present
waveforms of jvp
A - Pre-systolic: contraction of the right atrium
C - As the right ventricle contracts, the tricuspid valve closes and bulges into the right atrium (also the point at which the carotid pulse is palpable)
V - At the end of ventricular systole, venous return fills the right atrium passively against a closed tricuspid valve
The A and V waves can be identified by timing the double waveform with the adjacent carotid pulse. The A wave will occur just before the carotid pulse and the V wave occurs towards the end of the carotid pulse. check google for image
waveforms of jvp - descents
X - pressure drops as the right atrium relaxes
Y- the tricuspid valve opens and blood flows passively into the right ventricle (google image)
from where do you measure JVP
The JVP is measured with the patient sitting at a 45 degree angle and height is measured from the sternal notch. The normal JVP is 4cm in height from the sternal notch.
Causes of elevated JVP
Right ventricular failure
Tricuspid regurgitation or stenosis
Pericardial effusion or constrictive pericarditis
Superior Venous Cava obstruction
Volume overload (there are many reasons for this, congestive heart failure, renal failure, iatrogenic)
Grades of murmurs
A Grade 4 murmur is a loud murmur with a palpable thrill. Based on the intensity of a murmur it may be classified into the four following grades:
Grade 1: The murmur is heard only on listening intently for some time.
Grade 2: A faint murmur that is heard immediately on auscultation.
Grade 3: A loud murmur with no palpable thrill.
Grade 4: A loud murmur with a palpable thrill.
murmurs
sounds created by abnormal, turbulent flow of blood in the heart
bruits
unusual sound, usually abnormal, heard in auscultation
is a murmu from outside the heart eg AAA
Reynolds number
The ratio of inertial forces to viscous forces.