This document discusses the use of atropine as an adjunct to exercise stress testing and dobutamine stress echocardiography. Atropine is an anticholinergic drug that causes a rapid increase in heart rate and has been used in pharmacological stress test protocols. The document outlines an atropine protocol where subjects unable to reach their target heart rate during exercise stress testing are given intravenous doses of atropine to help induce ischemia and increase diagnostic sensitivity. Recent studies have also combined low doses of atropine and dobutamine as an alternative pharmacological stress test.

1. ATROPINE TEST
By: Manjoosha
Asst. Professor
CVT, MAHE

2. INTRODUCTION
• Exercise as well as pharmacologic stress testing is used for the
noninvasive detection of obstructive coronary artery disease (CAD)
based on the presence of stress-induced myocardial ischaemia
• Compared with pharmacological stress testing, exercise stress testing
has a higher sensitivity and specificity in detecting CAD in subjects
who have an adequate chronotropic response to exercise

3. INTRODUCTION
• In order to assess for inducible ischaemia, patients must be able to
exercise to achieve at least 85% of their maximum age-predicted
heart rate (MPHR)
• However, a significant number of subjects (23–39%) do not reach
their target heart rate (THR), either due to chronotropic
incompetence or due to sub-maximal exercise capacity

4. INTRODUCTION
• Pharmacological stress testing with dobutamine is used to induce
ischaemia by triggering an increase in myocardial oxygen demand
through an increase in the heart rate (HR) and rate pressure product
(RPP)
• Atropine is an anticholinergic drug that also causes a rapid increase in the
HR, and has been commonly used in pharmacological stress test protocols

6. Atropine dose
• The safety of intravenous atropine in doses ranging from 0.5 to 2 mg and
its use with dobutamine as an adjunct to augment HR have been studied
and validated
• Supine bicycle exercise stress echocardiography (SBESE) has the
advantage of allowing echo assessment of sequential wall motion during
exercise and at peak exercise, and avoids a drop in the HR during peak
exercise and imaging as occurs with treadmill stress echo

7. Atropine protocol
• Subjects who are unable to reach target HR, atropine will be given
intravenously in doses of 0.4 mg each 1 min apart, up to a maximum
of 1.2 mg with continuous ECG monitoring
• Any adverse events associated with atropine administration will be
recorded

8. Chronotropic response
• Chronotropic incompetence is failure to achieve 85% of the age-
predicted maximum heart rate at maximum exercise capacity during EST
• Poor exercise capacity (inability to reach an exercise level of at least 6
metabolic equivalents or METS), likewise limits the utility of the exercise
testing

9. EST
• In routine practice, when a patient is unable to achieve THR during
EST and has not demonstrated symptoms or electrocardiographic
changes indicative of ischemia or has poor exercise capacity, the test
is reported as inconclusive EST and usually, the patient are reffered
for dipyridamole nuclear stress testing or dobutamine stress
echocardiography which adds to cost

10. Uses
• Atropine has been shown to increase the overall diagnostic
sensitivity of dobutamine stress echocardiography
• Dipyridamole has also been combined with atropine for stress testing,
but addition of atropine to EST, due to poor exercise capacity or
chronotropic incompetence has not been proved

11. Other uses
• An alternative pharmacological stress, which consists of premedication
with 50 mg/kg atropine IV followed by an incremental challenge of low-
dose dobutamine, has recently been studied
• It allows a reduction in the required dobutamine dosage by almost a
factor of ten to obtain a cardiac stimulation comparable to that achieved
using high dosages of dobutamine alone without inducing adverse effects
such as cardiac arrhythmias, trembling, coughing, and restlessness