There are approximately 1.5 million major operations carried out in the NHS every year.
As the population ages, and surgical technique becomes more advanced, more patients are
undergoing operations which carry a high risk of complications. Currently, doctors
predict this risk by asking patients about medical problems and their level of physical
fitness. If an operation is very high risk, a patient may undergo cardiopulmonary
exercise testing (CPET) where the patient rides an exercise bike to maximum effort
(exhaustion) whilst their heart and lung function is measured. This gives the doctor
specific numbers which can be discussed with the patient about the risk of complications
after surgery. However, CPET is expensive and not all patients are able to do it, for
example due to joint or circulation problems. Patients can also find attempting to reach
maximal effort demanding and uncomfortable.
Heart rate recovery (HRR) after maximal exercise has been shown to indicate
post-operative risk of complications, and is also related to life-expectancy in people
with heart failure. The utility of HRR after submaximal exercise however has not been
investigated as extensively. One group demonstrated that submaximal HRR predicts
post-operative complications after lung surgery, and submaximal HRR also predicts
life-expectancy in healthy individuals. There is less information about submaximal HRR as
the methods of measuring it are not standardised. Previous work by our group has
confirmed the reproducibility of submaximal HRR in a healthy population, and demonstrated
different ways in which to measure it. The investigators believe that submaximal HRR
provides a "middle-ground" method of assessing how fit a patient is for surgery.
With informed consent, 95 patients across four hospitals in the West of Scotland will
perform a step test pre-operatively. The step test will involve non-invasive measurement
of the heart rate. Patients will exercise until approximately two-thirds of their
predicted maximum heart rate is reached and then recover sitting, whilst the rate of
their heart rate recovery is recorded. Patients will have pre- and post-operative
troponin values measured (blood marker of strain/injury to the heart). Alongside the
blood tests, patients will also answer questionnaires related to their quality of life,
and information regarding other post-operative complications will be recorded.
The study aims to demonstrate that submaximal HRR is predictive of post-operative
myocardial injury (stress/injury to the heart wall due to the body's response to the
operation) and that is it a valid measure when compared to the scores, blood tests and
exercise tests that are currently in use in the NHS. In the future, submaximal exercise
testing with HRR measurement may be offered to patients unable to perform CPET and will
guide shared decision-making between patient, surgeon and anaesthetist to ensure the best
outcome for the patient regarding their surgical options.