Cardiac changes Flashcards
who should be excluced from the exercise part
Unstable angina Resting SBP>200mmHg or DBP >110mmHg Uncontrolled tachycardia >120b.min-1 Significant resting ST segment depression Uncontrolled atrial or ventricular arrhythmias Aortic stenosis Febrile illness Recent embolism Uncompensated congestive heart failure
why does SV increase in healthy individuals following areobic training
↑ contractile function
↑ LV chamber volume (eccentric)
↑ LV muscle mass (concentric)
↑ in plasma volume
why does contractile function increase
• ↑ calcium handling proteins in cell wall and SR
why does LV chamber volume increase
Myocyte elongation as sarcomeres added in series: occurs after 5 weeks
why does LV muscle mass increase
More myocytes added in parallel (hypertrophy)
why does plasma volume increase
10% PV expansion may occur in just 10 days
la place’s law
T = ( P * R ) / M
• Where T is the tension in the walls • P is the pressure difference across the wall • R is the radius of the cylinder • M is the thickness of the wall
To keep wall tension the same, the radius and the wall thickness must be proportional
what alters myocradial oxygen consumption
tennison development
myocardial contractility
heart rate
- wall tension is an imporatant determinant of MVO2
what causes growth
NE and Epinephrine Renin-angiotensin-aldosterone GH and IGF Thyroid hormones mechanical stress
effect of NE and Epinephrine
Growth
stimulation of alpha and beta receptors in the myocardium cause cardiac growth
effect of Renin-angiotensin-aldosterone
Growth
– ↑ SNS activity reduces renal blood flow during exercise, ↑ renin release, thus ↑ RAA levels
– ↑ RAA levels stimulate cardiac myocytes to hypertrophy
effect of GH and IGF:
Growth
Cardiac myocytes have receptors for both GH and IGF
– Stretching of heart muscle is trigger for these hormones to activate gene expression
– IGF increases myofilament sensitivity to Ca++ thus ↑ contractile forc
what is the effect of thyroid hormones
Growth
Exercise stimulates TSH, thus thyroxin production
Thyroxin causes myocyte hypertrophy
effect of mechanical stress
Pressure overload = ↑ resistance = hypertrophy through ↑ cross sectional area (Concentric)
↑ volume overload = hypertrophy through ↑ myocyte lengthening (Eccentric)
Mechano-sensors in myocyte activated by stress:
– Surface receptors (integrins) and stretch activated ion channels ↑ CA++ influx → activate protein kinase pathways → hypertrophy
Physiological adapltaions to areobic training in healthy individuals
imporved contractility
Angiogensis
effect of imporved contracitility
Improved % shortening, time to peak shortening, relaxation time – ↑ calcium binding sites in myocytes – ↑ Na+ - Ca++ exchanger pumps speed removal of Ca back into SR – ↑ Ca stored in SR = more Ca = more contractile force – ↑ Ca sensitivity of myofilaments • Increased ATPase expression
effect of Angiogensis
Myocyte hypertrophy comes with angiogensis to increase blood flow • Increased arterial size to be equal or greater than increase in cardiac mass (over adaptation!) • Increased capillarisation
adaptaions to areobic training cardiovascular
Stroke volume
↑ Stroke volume 0 - 18% – ↑ blood volume 6-10% – Myocardial hypertrophy – Improved contractile force - ↓ ESV – ↑ ejection fraction
adaptaions to areobic training cardiovascular
parasympathetic tone
increased parasympathetic tone
• ↑ Heart rate variability
• Slower heart rate, thus more filling time
adaptaions to areobic training cardiovascular
↑ SV ↑ parasympathetic tone ↑ coronary collaterals ↑ in cardiac capillary and arteriole blood flow ↓ blood viscosity ↓ endothelial dysfunction
why does endothelial dysfunction reduce
Improved NO production promotes vasodilation
• Improved production of superoxide dismutase which mops up Reactive Oxygen Species (ROS stops NO working)
adaptaions to areobic training cardiovascular during exercise
↑ in max SV
↓ In sub-maximal exercise heart rate - but this may arise without increase in SV
↓ Systolic blood pressure response
↑ Nitric oxide production, ↑ vasodilation thus ↓ TPR
↓ In myocardial oxygen demand (measured by RPP)
Small ↓ in Submax exercise Q
Improvement in max cardiac output
↑ Arteriovenous difference - more O2 extracte
adaptaions to muscle from areobic training cardiovascular
↑ Arteriovenous difference
- V. important as may cause ↑ in peak VO2 without ↑ in Q.
↑ Mitochondrial number and quantity of aerobic enzymes
Shift towards a more aerobic muscle fibre type profile
↓ submaximal exercise muscle blood flow because of ↑ usage of delivered O2
↑ Maximal muscle blood flow
↑ Muscle capillary density
↑ Muscle fibre recruitment
↓ Blood lactate concentration during sub-maximal exercise
effect of 1 MET increase
15% better surival
effect of aerobic training on total exercise capacity
18-35% increase
effect of aerobic training on angina threshold
10-20% increase
activity during first 48hrs following MI/surgery
Self Care Activities
Arm and leg range of motion movement
Low Resistance activities
Minimal activities - active remodelling of myocardium occurring. Don’t want to exacerbate damaged area
what should the patinet have knowledge of before dischange
Activities that are inappropriate or excessive
a safe progressive plan of exercise
optimal risk reduction
why should they do activity post discharge
Physiological benefits
Increase physical self confidence
Decrease dependency on others
rules of walking psot discharge
Walk at a comfortable pace (RHR + 20bpm) Take GTN spray Know rules of chest pain Choose flat route Go with someone at first Once solo, let others know the route
post discharge walking week 1
1/4 mile
4 days
post discharge walking week 2
1/2 mile
4 days
post discharge walking week 3
3/4 mile
4-5 days
post discharge walking week 4
3/4 mile
4-5 days
post discharge walking week 5 &6
1 mile
5 days
postive end points of exercise stress test
Reaching estimated max HR ± 10bts.min-1 Light headedness, confusion, ataxia, cyanosis, dysponea, nausea Onset of moderate – severe angina Symptomatic SVT ST depression >2mm ST elevation >1mm VT Exercise induced LBBB Onset of 2nd or 3rd degree heart block Hypotension (>10mmHg drop in BP) Hypertension (>220 mmHg SBP : >110mmHg DBP) Inappropriate bradycardia (drop in HR >10 beats / min) with increase or no change in work load
sensivity of exercise stress test
Sensitivity and specificity of stress test for diagnosis of CAD approx. 70%
The above may be better / worse due to expertise / equipment / population
what is sensitivty
Sensitivity = % with disease who have abnormal results (test picks up something is wrong here!)
what is specificity
% without disease who have normal results (test picks out healthy by showing normal results)
prescribing exercsie using HR
etermine peak HR from test data
The highest HR achieved before problems (Angina etc)
Calculate training heart rate zone: 40-80% of the peak HR value
use common sense
exercise prescriptin hreat rate reserve
Heart rate reserve (HRR) may be used if no stress test data are available
– however if stress test HR data are available HRR can still be used
Allows calculation of training HR zone
Scope to increase HR (HRR = predicted max HR - resting HR) + resting HR
Suggested 40-80% HRR
calculating peak HR
Healthy males = 208 – (0.7 x age)
Healthy women = 206 – (0.88 x age)
CAD patients = 164 – (0.72 x age)
β-blocked = 203-1.49(age)
exercise prescrpition RPE
RPE may be used to set training exercise intensity
A scale to quantify how hard the patient feels he / she is working
Roughly 12-16
Habituation necessary
effect of anti-arrythmics of HR, BP, ischemia and exercise
HR ↓ or↔
BP ↔
Ischemia↔
Exercise capacity ↑
effect of anticoagulants on HR, BP, ischemia and exercise
HR ↔
BP ↔
Ischemia↔
Exercise capacity ↔
effect of ACE inhibitors on HR, BP, ischemia and exercise
HR ↔
BP ↓
Ischemia↔
Exercise capacity ↔
effect of antilipidepics on HR, BP, ischemia and exercise
HR ↔
BP ↔
Ischemia↔
Exercise capacity ↔
effect of digoxin on HR, BP, ischemia and exercise
HR ↓
BP ↔
Ischemi - maybe st depression
Exercise capacity ↔ or ↑
effect of beta blockers on HR, BP, ischemia and exercise
HR ↓
BP ↓
Ischemia ↓
Exercise capacity ↑ or ↓
effect of calcium channel blockers on HR, BP, ischemia and exercise
HR ↓
BP ↓
Ischemia↓
Exercise capacity ↑
effect of nitrates on HR, BP, ischemia and exercise
HR ↑
BP ↓
Ischemia ↓
Exercise capacity ↑
effect of diureactics on HR, BP, ischemia and exercise
HR ↔
BP ↓
Ischemia↔
Exercise capacity ↔
describe the effect of digoxin
May decrease exercise HR • Improve exercise capacity in patients with atrial fibrillation or chronic heart failure • May produce false-positive results on the ECG, or ST segment depression in patients without coronary artery disease or ischemia. Use should be stopped 10 to 14 days prior to exercise test if possible
describe the efefct of beat blockers
Addition or change in dosage of beta-blocker will require a new graded exercise test • Relationship between %VO2 and %HRR is not altered; therefore, usual methods to calculate THR for exercise prescription are still acceptable • HRmax and training HR will be lower in persons receiving beta-blockers
describe the effect of calcium channel blockers
May length PR interval – facilitates Ventricular filling • Meds change will alter exercise response so new max test may be needed
describe the efects of nitrates
Increases angina threshold • Possible hypotension • Longer cool down to avoid post-exercise hypotension
describe the role of diuretcis
Diuretics may lower potassium levels (Hypokalaemia) – leads to PVC’s
Possible hypovolemia – will lower BP, Q and capacity – so check hydration status
walk as exercise
lesuire or CV
Walking speed should achieve HR in training zone Pleasurable
Golf as exercise
METS 4-7 Aerobic / anaerobic Flat course 9 Holes at first, ↑ number slowly 3/4 swing Half set of clubs Pull or carry clubs Chest pain rules
Bowls as exercise
Bowls has NO cardiovascular benefit
But will improve coordination, flexibility and confidence in physical activity
Swimming as exercise
No swimming until sure of arrhythmia / angina / wound status METS 4 - 8 Is HR in training zone? Vary stroke Chest pain rules Cold water
who is strength training not appropriate for
Congestive Heart Failure Severe Valvular Disease Low ejection fractions Uncontrolled Arrhythmias Significant left ventricular dysfunction
blood pressure response during resistance training
↑ intra muscular pressure ↓ muscular blood flow ↑intrathoaracic pressure ↓ Venous return ↓ → Q ↑ ↑TPR = ↑BP
acute effects of resistnce training
↑ BP ⇒ ↑ RPP (HR X SBP∴MVO2) not problematic if < 80% 1RM ↑ HR 60-80% HR max during circuit weights ↑ VO2 30-50% VO2max during circuit weights
what does strength training response depend on
Type (isotonic / isometric) Weight lifted (% 1RM) Duration of rest intervals Starting CV fitness of person Medications
chronic eefcts of strength training
Muscular strength ↑ 20-30% in cardiac patients ↑ efficiency of movement Small ↑ in peak VO2 Improved blood lipid profile ? Improvement in body composition ? Reduction in BP
when should you use resistnce training
Start 4-6 weeks into supervised cardiorespiratory endurance exercise program
into supervised cardiorespiratory endurance exercise program
Use elastic bands, light handweights, or resistive tubing to add variety
Monitor heart rate and ECG continually
