TMT

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TMT
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EXERCISE PHYSIOLOGY

• Vagal withdrawl-increased HR
• Symp activation-increased venous return
• -increased ventilation
• -increased HR
• Increase in CO, BP

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MET Values

• 1 MET "Basal" 3.5 ml O2 /Kg/min
• 2 METs 2 mph on level
• 4 METs 4 mph on level

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• 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

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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
  

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• 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.

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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 5grade. 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
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• Formula to estimate VO2 from treadmill speed and
  grade is
• Vo2 (ml O2/kg/min)(mph 2.68) (1.826.82mphgra
  de/100)3.5

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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
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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
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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.
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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
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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
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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. lt0.7-1mv /sec), 80 msec after J point
(ST 80) in 3 consecutive beats with a stable
base line is considered to be abnormal response
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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
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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 Developme
nt 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
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Blood pressure 1.Normal exercise response is to
increase systolic BP progressively with
increasing workloads. In normal persons
diastolic BP doesnt change significantly 2.Failu
re to increase systolic BP beyond 120mm Hg, or a
sustained decrease greater than 10 mmHg is
abnormal
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• 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

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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 85of 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
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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-(5ST deviation)-(4treadmill angina
index) Angina index- 0-if no angina 1-if typical
angina occurs during exercise 2-if angina was the
reason pt stopped exercise lt5-low riskno
coronary art stenosis or svd-5yr survival of
97 -10 to4 -moderate risk --- 5yr survival of
91 gt11 high risk 3vd or Lt main CAD- 5yr
survival of 72
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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
20-35 mmHg beats/min 10-3 Chest
discomfort Chest discomfort usually occurs after
the onset of ST segment abnormality
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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
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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
(gt10 METS) have excellent prognosis regardless
of anatomical extent of CAD.
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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
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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.
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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
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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.
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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.
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Supraventricular arrythmias Premature beats are
seen in 4-10of normal persons, 40of patients
with underlying heart disease. Sustained
arrythmia occur in 1-2. May approach 10-15 in
patients referred for management of episodic
arrythmias.
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• 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.

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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
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• 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

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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
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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.
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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
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Elderly patients Test should be started at
slowest speed with 0 grade and adjusted
according patients 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
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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.
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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.
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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(lt1mon). 6-12 mon post procedure
test helps to detect restenosis
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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
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Safety and risks of TMT Mortality is lt0.01,
morbidity is lt0.05 Relative risk of major
complication is twice when symptom limited
protocol is used as compared with low level
protocol
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