Download TMT

EXERCISE PHYSIOLOGY
• Vagal withdrawl-increased HR
• Symp activation-increased venous return
•
-increased ventilation
•
-increased HR
• Increase in CO, BP
MET Values
1 MET = "Basal" = 3.5 ml O2 /Kg/min
2 METs = 2 mph on level
4 METs = 4 mph on level


10 METs = As good a prognosis with
medical therapy as CABS
13 METs = Excellent prognosis, regardless
of other exercise responses

16 METs = Aerobic master athlete

20 METs = Aerobic athlete
Calculation of METs on the Treadmill
METs = Speed x [0.1 + (Grade x 1.8)] + 3.5
3.5
Calculated automatically by Device!
Note: Speed in meters/minute
conversion = MPH x 26.8
Grade expressed as a fraction
Exercise is a common physiological stress used to
elicit cardiovascular abnormalities not present at rest
and to determine adequacy of cardiac function.
TMT is the one of the most frequent noninvasive
modalities used to assess patients with suspected or
proven cardiovascular disease.
It is used to estimate the prognosis and to determine
functional capacity, the likelihood and extent of CAD
& effects of therapy.
Tread mill protocol
1.Bruce multistage maximal treadmill protocol has
3min periods to achive steady state before workload is
increased. In older individuals or those whose exercise
capacity is limited, it can be modified by two 3 min
warm up stages at 1.7mph and 0 percent grade and
1.7mph and 5%grade.
2.The Naughton and Weber protocols use 1-2min stages
with 1-MET increments between stages,
3.Asymptomatic cardiac ischemia pilot trial and
modified ACIP protocols use 2min stages with 1.5mets
increments between stages after two 1min warm up
Formula to estimate VO2 from treadmill speed and grade
is
Vo2 (ml O2/kg/min)=(mph *2.68)
+(1.8*26.82*mph*grade/100)+3.5
Technique
1.Patients should be instructed not to drink,eat caffeinated
beverages or smoke 3hr before testing & to wear
comfortable shoes and clothes.
2.Unusual physical exertion should be avoided
3.Brief history & physical examination should be
performed
4.Should be instructed about risks and benefits
5. Informed consent is taken
6.12 lead ECG is recorded with electrodes at the distal
extremities
8.Torso ECG is obtained in standing and sitting position
9.If false +ve test is suspected,hyperventilation should be
performed
11.Area of electrode application should be rubbed with
alcohol saturated pad to remove oil and rubbed with
sand paper to reduce skin resistance to 5000ohms or less
12.cables should be light flexible and shielded
13 room temp should be 18 –24 C & humidity less than
60%
13.walking should be demonstrated to the patient
14.HR, BP & ECG should be recorded at the end of each
stage.
15.Minimum of 3 leads should be displayed continuously
on the monitor
16.A resuscitator cart, defibrillator and appropriate
cardioactive drugs should be available in the TMT room.
17. IV line should be started in high risk patients.
Lead system:
1.Arm electrodes should be located in the most lateral aspect
of infra clavicular fosse & leg electrode should be above ant
iliac crest and below rib cage
2.bipolar lead groups place the negative electrode over
manubrium(CM5), right scapula (CB5), RV5 (CC5),or on
the forehead (CH5) and active electrode at V5
1.In myocardial ischemia, ST segment becomes horizontal,
with progressive exercise depth of ST segment may increase
2.In immediate post recovery phase ST segment displacement
may persist with down sloping ST segments and T wave
inversion returning to baseline after 5-10 min
3.In 10% , ischemic response may appear in recovery phase
1. PQ junction is chosen as isoelectric point , TP segment is
true isoelectric point but impractical choice
2. Development of 0.1mv (1mm) or greater of ST segment
depression measured from PQ junction with a relatively flat
ST segment slope (e.g. <0.7-1mv /sec), 80 msec after J point
(ST 80) in 3 consecutive beats with a stable base line is
considered to be abnormal response
3.When ST 80 measurement is difficult to determine at
rapid heart rates ST 60 measurements should be used
4.when ST segment is depressed at rest, j point or ST 80
measurements should be depressed an additional 0.1mv
or more, to consider abnormal
Upsloping ST segment
In patients with high CAD prevalence, slow up sloping ST
segment depressed 0.15mv or greater at 80msec, after J point
is considered abnormal
ST segment elevation
Development of 0.1mv ( 1mm) or greater of J point
elevation, at 60msec after J point in 3 consecutive beats with
stable baseline is considered abnormal response.
Occurs in 30% of AWMI & 15% of IWMI
When it occurs in non q wave lead in a patient without
previous MI it indicates transmural ischemia caused by
coronary spasm or high grade coronary narrowing.
ST elevation is relatively specific for territory of ischemia
Blood pressure:
1.Normal exercise response is to increase systolic BP
progressively with increasing workloads. In normal persons
diastolic BP doesn’t change significantly
2.Failure to increase systolic BP beyond 120mm Hg, or a
sustained decrease greater than 10 mmHg is abnormal
Heart rate response
Sinus rate increases progressively with exercise.
Inappropriate increase in heart rate at low exercise work
loads may occur in patients who are in AF,physically
deconditioned, hypovolumic, anemic, or have marginal left
ventricular function
Chronotropic incompetence is determined by decreased heart
rate sensitivity to the normal increase in sympathetic tone
during exercise and is defined as inability to increase heart rate
to at least 85%of age predicted maximum. Heart rate reserve is
calculated as
Chronotropic index refers to heart rate increment per stage
of exercise that is below normal.
It indicates autonomic dysfunction, sinus node disease, drug
therapy(beta blockers), myocardial ischemic response.
When chronotropic index is less than 80%, long term
mortality is increased
Tread mill (TM) score: is designed to provide survival
estimates based on results from exercise test. Provides accurate
prognostic & diagnostic information
TM score:
Exercise time-(5*ST deviation)-(4*treadmill angina index)
Angina index0-if no angina
1-if typical angina occurs during exercise
2-if angina was the reason pt stopped exercise
<5-low risk:no coronary art stenosis or svd-5yr survival of 97%
-10 to+4 :-moderate risk --- 5yr survival of 91%
>11– high risk: 3vd or Lt main CAD:- 5yr survival of 72%
Rate-pressure product
Heart rate –systolic BP product increases progressively with
exercise and peak rate pressure product can be used to
characterize cardiovascular performance.
Normal individuals develop peak rate-pressure product of 2035 mmHg *beats/min* 10-3
Chest discomfort
Chest discomfort usually occurs after the onset of ST segment
abnormality
1.Sensitivity in patients with CAD is 68% and specificity is
77%
2.In SVD -- sensitivity is 25-71%
3.In multivessel CAD-- sensitivity is 81%, specificity is 66%
4.Left main or 3vd -- sensitivity is 86%, specificity is 53%
Asymptomatic population
Prevalence of abnormal TMT in asymptomatic middle
aged men ranges from 5-12%.
Appropriate asymptomatic subjects would be those with an
estimated annual risk greater than 1 or 2% per year.
Symptomatic patients
Exercise should be routinely performed in patients with
chronic ischemic heart disease before CAG.
Patients who have excellent effort tolerance (>10 METS)
have excellent prognosis regardless of anatomical
extent of CAD.
Salient myocardial ischemia
In patients with documented CAD, exercised induced ST
segment depression confers increased risk of subsequent
cardiac events
Acute coronary syndrome
Incidence of angina or ST segment abnormalities in these
patients ranges from 30-40%.
ST segment changes or chest pain is associated with
significantly increased risk of subsequent cardiac events
After MI
Exercise testing is useful to determine
1.risk stratification and assessment of prognosis
2.functional capacity for activity prescription
3.assessment of adequacy of medical therapy & need to use
supplemental diagnostic or treatment options
Ability to complete 5-6METS of exercise or , 70-80% age
predicted maximum in the absence of abnormal ECG or BP is
associated with 1 year mortality rate of 1-2%.
Preoperative risk stratification before non-cardiac surgery
It provides measurement of functional capacity and potential
to identify the likelihood of perioperative ischemia in patients
with low ischemic threshold
Cardiac arrythmias & conduction disturbances
VPCs are common during exercise test & increase with age.
Occur in 0-5% of asymptomatic subjects.
Suppression of VPCs during exercise is nonspecific.
20% of patients with known heart disease and 50-70% of
sudden cardiac death survivors have repetitive ventricular
beats induced by exercise.
In patients with recent MI, presence of repetitive forms is
associated with increased risk of cardiac events.
5 yr all cause mortality is higher in patients who have frequent
ectopics in recovery phase.
Test is useful in evaluating :
1.effects of antiarrhythmic drugs
2.detecting supraventricular arrhythmias
3.treating patients with chronic AF to test for ventricular
rate control
4.possible drug toxicity in patients on antiarrhythmic drugs
Evaluation of ventricular arrythmia
1.Exercise testing provokes VPCs in most patients
with sustained ventricular tachyarrythmia.
2.VPC that occurs in the early post exercise phase is
associated with worse long term prognosis.
Supraventricular arrythmias
Premature beats are seen in 4-10%of normal persons, 40%of
patients with underlying heart disease.
Sustained arrythmia occur in 1-2%. May approach
10-15% in patients referred for management of episodic
arrythmias.
Atrial fibrillation
Rapid ventricular response is seen in initial stages of exercise.
Sinus node dysfunction
Lower heart rate response is seen at submaximal and maximal
workloads.
Atrioventricular block
In congenital AV block, exercise induced heart rate is low .
Some develop symptomatic rapid junctional rhythms.
In acquired diseases, exercise can elicit advanced AV block.
LBBB
ST depression is seen in patients with LBBB
& cant be used as diagnostic indicator.
Relative risk of death or other major cardiac events in these
patients is increased three fold.
RBBB
Exercise induced ST depression in leads V1-V4 is common in
patients with RBBB and is non-diagnostic
In patients with RBBB
• 1.new onset ST depression in V5 & V6, or L II or avF
• 2.reduced exercise capacity
• 3.inability to adequately increase systolic BP
-------indicate presence of CAD.
New development of exercise induced RBBB is uncommon
(0.1%)
Preexcitation syndrome
Presence of WPW syndrome invalidates the use of ST
segment analysis as a diagnostic method.
False +ve ischemic changes are seen
Exercise may normalise QRS complex with disappearance of
delta waves in 20-50%
Exercise induced disappearance of delta wave is more frequent
with left sided than right sided pathway
Cardiac pacemakers and ICD
Test is useful in
1.Evaluating sensor trigger rate adaptive pacing
2.To assess performance following CRT in patients with heart
failure and ventricular conduction delay
Influence of drugs and other factors
In cold sensitive individuals, cooler environment results in
earlier onset of ST depression.
Cigarette smoking reduces ischemic response threshold.
Hypokalemia & digoxin are associated with exertional ST
depression
Nitrates, beta blockers, calcium channel blockers can prolong
the time to onset of ischemic ST depression, increase exercise
tolerance, and may normalize exercise ECG response in
documented CAD patients.
Women
Diagnostic accuracy is less in women due to lower prevalence
and extent of CAD.
False +ve results are common during menses or preovulation,
& in postmenopausal women on estrogen therapy
Elderly patients
Test should be started at slowest speed with 0% grade and
adjusted according patient’s ability
Frequency of abnormal results is more and risk of cardiac
events is also more
Diabetes mellitus
In patients with autonomic dysfunction and sensory
neuropathy anginal threshold is increased and abnormal heart
rate and BP response is common
Probability of adverse cardiac outcome is increased
Valvular heart disease
Exercise test can provide information on timing of operative
intervention and to estimate degree of incapacitation
Hypotension during test in asymptomatic patients with AS is
sufficient to consider for valve replacement.
In patients with MS, excessive HR response to relatively low
levels of exercise, reduction of cardiac output, and chest pain
are indicators that favour earlier valve repair.
In MVP without regurgitation at rest, exercise induced MR is
associated with subsequent development of progressive MR.
In HCM peak VO2 and anerobic threshold are reduced.
Inability to increase BP by 20mmHg is asso with adverse
prognosis
Coronary bypass grafting
ST depression may persist when incomplete
revascularisation is achieved and also in 5% of persons in
whom complete revascularisation is achieved.
Significant increase in exercise capacity is seen when large
amount of dysfunctional but viable myocardium is
revascularised
Percutaneous coronary intervention
Exercise ECG has low diagnostic accuracy to detect restenosis
in the early phase(<1mon).
6-12 mon post procedure test helps to detect restenosis
Cardiac transplantation
A peak VO2 of less than 12-14ml O2/kg/min or 40-50% of
predicted VO2 is associated with 2 year survival rates from
30-50%
Maximal O2 uptake & work capacity are reduced as compared
with age matched controls but improved as compared with
pre-operative findings.
Abnormalities that may be seen are
1.resting tachycardia
2.slow HR response during mild to moderate exercise
3.more rapid HR response during more strenous exercise
4.more prolonged time for ventricular rate to return to
baseline during recovery
Safety and risks of TMT
Mortality is <0.01%, morbidity is <0.05%
Relative risk of major complication is twice when symptom
limited protocol is used as compared with low level protocol