ECG and BP Flashcards
HR recording: 6-lead ECG
Used for:
- Athletes over 35yrs; and
- Asymptomatic, low risk individuals over 35yrs.H
HR recording: 12-lead ECG
Used for:
- All other individuals over 35yrs, who have cardiorespiratory signs, symptoms, multiple risk factors or medical conditions.
Cardiac conduction system (1)
specific conduction pathways allow for coordinated transmission of ____ _____ through the _____
action potentials
heart
Cardiac conduction system (2)
An action potential is created by the
sinoatrial (SA) node
Cardiac conduction system (3)
the signal spreads across the ___ causing them to ____, before reaching the _______ _____, where it is delayed allowing the ventricles to fill.
atria
contract
atrioventricular (AV) node
Cardiac conduction system (4)
it then travels to the ___ ___ ___, then along the inter-ventricular septum via the left and right bundle branches, then spreads along the ventricles via the ___ ___ causing them to contract.
bundle of His
Purkinje fibres
Cardiac conduction system (5)
What is captured by ECG?
Depolarisation (contraction); and
Repolarisation (relaxation)
…of cardiac muscle
ECG Lead V1
Fourth intercostal space just to the right of the sternal border
Septum
ECG Lead V2
Fourth intercostal space just to the left of sternal border
Septum
ECG lead V3
At the midpoint of a straight line between V2 and V4
Anterior
ECG lead V4
On the midclavicular line in the fifth intercostal space
Anterior
ECG lead V5
On the anterior axillary line and on a horizontal plane through V4
Lateral
ECG lead V6
On the midaxillary line and on a horizontal plane through V4 and V5
Lateral
BP reading consists of two figures ___ and ___, with the difference between the two being
systolic
diastolic
pulse pressure
for adults, typical systolic BP ranges between
120 and 145 mmHg
for adults, typical diastolic BP ranges between
60 and 85 mmHg
if BP exceeds normal range
high = hypertension
if BP is below normal range
low = hypotension
Measuring BP in individuals with coronary artery disease
- Combining BP and HR measures allows us to estimate cardiovascular stress that can be sustain during exercise.
- Coronary artery disease = imbalance between oxygen demand and supply to the heart - narrowing or blockage of coronary arteries which then limits supply of oxygenated blood to the heart.
- when heart oxygen supply is insufficient to meet demands (myocardial ischemia)
- angina, excessive shortness of breath, fatigue, palpitations or abnormally fast heartbeat, onset of nausea or need to vomit.
Measuring BP in individuals with coronary artery disease
we cannot measure myocardial oxygen supply during a standard stress test, but we can estimate myocardial oxygen demands using the rate pressure product (RPP) formula
RPP = heart rate (bpm) x systolic blood pressure (mmHg)
- oxygen demand depends on how fast and frequently a muscle is contracting (heart rate) and how much force it needs to contract with (systolic BP)
- calculated at each stage of the stress test.
- onset of ischemia or symptoms can indicate severity of disease.
YMCA cycle test protocol
- determine age-predicted max HR and criteria for terminating exercise test
- setup bike with correct positioning
- collect resting HR and BP
- 25 watts, 50rpm for 3 min
- based on HR at end of first stage, use the table to decide subsequent work rates for next 3 stages
- 3 mins per stage, collect HR and BP, monitor for ST-depression at each stage
ECG criteria for stopping an exercise test (absolute - must stop)
- technical difficulties in monitoring ECG tracings
- sustained ventricular tachycardia
- ST-elevation of more than 1mm in leads without Q waves
ECG criteria for stopping an exercise test (relative)
- ST or QRS changes (excessive horizontal or downsloping ST depression of more than 2mm)
- Arrhythmias
BP criteria for stopping an exercise test (absolute - must stop)
- drop is systolic BP of greater than 10 mmHg from baseline when accompanied by other indications of ischemia.
- technical difficulties in monitoring systolic BP
