Pre-operative exercise capacity

Patient safety is the primary concern when assessing exercise capacity before scheduled cardiac surgery. Underlying cardiac disease may contraindicate the performance of objective tests as cardiac ischaemia and arrhythmia can commonly occur during testing prior to surgery.[#hirschhorn-ad.-2010]

In patients at risk of ‘silent’ cardiac ischaemia (e.g., with diabetes, severe coronary artery disease), the cardiologist and/or cardiac surgeon should be consulted before attempting objective assessment, and strong consideration should be given to ECG-monitoring throughout and after the assessment.

Self-paced tests such as the 6-minute walk test (6MWT) may be preferable than externally paced tests, such as the incremental shuttle walk test (ISWT). Safety of the 6MWT in patients awaiting CABG has not been established and if there are concerns about safety, the 6MWT may be substituted with a 2-minute walk test or a modified 6-minute walk assessment.[#brooks-d-parsons-j-tran-d-et-al.-2004,#hirschhorn-ad-richards-d-mungovan-se-et-al.-2008]

Inpatient post-operative exercise capacity

The standard 6MWT or modified 6MWT assessment are two feasible options for the assessment of exercise capacity at hospital discharge. If a walk test has been performed prior to surgery, a repeat walk test at hospital discharge will provide information that can be used to benchmark early and relative recovery of exercise capacity and provide a baseline before commencing post-acute exercise rehabilitation.

The presence of physiological factors that may reduce exercise capacity in the early post-operative period should be assessed and recorded.

These may include:

• Anaemia
• Impaired autonomic cardiac modulation
• Impaired ventricular function
• Deconditioning from bed-rest and/or limited physical activity (both before and after surgery)
• Alterations in respiratory function
• Fatigue (including that occurring from sleep deprivation)
• Post-operative pain

When to commence exercise

Post-surgical inpatient exercise of reasonable intensity can improve functional outcomes at discharge[#hirschhorn-ad-richards-d-mungovan-se-et-al.-2008,#van-der-peijl-id-vliet-vlieland-tpm-versteegh-mim-et-al.-2004].

Assuming that the patient is haemodynamically stable (and that there are no other contraindications), walking, sitting out of bed and gentle ambulation (on the spot or for short distances within a monitored environment) are suitable during the first 48 hours.

The American College of Sports Medicine recommendations for intensity, duration, frequency and progression of exercise in hospital after cardiac surgery are as follows:[#american-college-of-sports-medicine.-2013]

Type of exercise

All patients should undertake a progressive walking program during the inpatient stay. During this time, some patients may be prohibited from using walking aids due to concerns that weight-bearing through the upper limbs may affect sternal union and healing.

Stationary cycling may provide an alternative mode of exercise for patients unable to walk independently without an aid, provided that the patient can easily mount and sit comfortably on the seat. One benefit of stationary cycling is that it may be easier to monitor the patient (ECG, blood pressure, etc.), and hence constrain or stop exercise if necessary.

For specific recommendations on thoracic and upper limb exercise during the post-operative phase, see sections on musculoskeletal management and sternal stability management.

Exercise monitoring during the inpatient phase

ECG

Following cardiac surgery, it is prudent to continue ECG monitoring with exercise during the early post surgical period, until otherwise confirmed by the cardiac surgeon or cardiologist [#drew-bj-califf-rm-funk-m-et-al.-2004]. AF occurs in approximately 30% of patients undergoing isolated CABG and approximately 60% of patients undergoing combined CABG and valve procedures.[#drew-bj-califf-rm-funk-m-et-al.-2004]  The onset of AF most commonly occurs between the second and fourth post-operative day, so in many institutions, ECG monitoring (e.g., via telemetry) is continued for at least the first 4 days.  Patients with AF, particularly with rapid ventricular response ( >100 beats per minute) are at risk of haemodynamic compromise during exercise. For these patients, exercise should be undertaken only when haemodynamically stable and should be limited to gentle walking, as tolerated. BP should be measured prior to mobilising and the patient monitored throughout for signs of hypotension, dizziness and fatigue.

 As ECG systems are often monitored at a central location (e.g., a nurse's station), it is useful to alert staff at this location when an exercise session is to be undertaken, so that the exercise  session can be stopped in a timely fashion if a cardiac arrhythmia/event occurs.

Peripheral oxygen saturation (SpO₂)

Intermittent or continuous SpO₂ should be measured during exercise using a portable pulse oximeter. Supplemental oxygen should be strongly considered during exercise if resting oxygen saturation is below 92%, or if the SpO₂ drops by 5% or more during exercise. Note that if a patient is in AF, it may be difficult to obtain an accurate SpO₂ measure.

Almost all patients experience respiratory dysfunction to varying degrees after cardiac surgery. Supplemental oxygen will often be needed during exercise in the first 48 to 72 hours.

Rating of perceived exertion

Prescribing exercise on the basis of HR alone is not recommended.  This is because there is considerable individual variance in resting HR, as well as HR response to exercise in the acute setting. Furthermore, HR response is influenced by various medications, particularly beta blockers. Use of the Rating of Perceived Exertion- Borg scales is often more appropriate for monitoring and prescribing exercise intensity than HR in these patients.

Percutaneous coronary intervention

Most patients can resume physical activity and exercise within a few days of their PCI unless obvious problems are evident. The underlying IHD is the main influence on exercise prescription; see previous section on ischaemic heart disease.

When prescribing exercise to patients with recent PCI, the following should be considered:

• Type of PCI and the risk of restenosis
• Discomfort at rest or on exertion at, or distal to, the site of peripheral artery cannulation
• Presence of angina symptoms at rest or on exertion
• The patient's compliance with anti-platelet medications.

Coronary artery bypass graft

Coronary artery bypass graft (CABG) is usually performed via surgical division of the sternum (i.e., median sternotomy). Post-operative complications include musculoskeletal problems related to the incisional scar (infection, hypersensitivity, hypertrophy) and sternal instability. Thorough assessment of these post-surgical factors is crucial to safe and effective exercise prescription.

Following a median sternotomy, the two sternal halves are usually approximated together using stainless steel wires in order to restrict any movement between the two bony edges to optimise healing. Minimal motion of the two sternal halves should only be present in the early weeks following this procedure.

There is no research regarding the length of time it takes for the sternum to heal. Therefore, it is important to correlate the findings from a subjective and physical examination and report any positive findings to the treating cardiac surgeon or general practitioner.

What is sternal instability?

Sternal instability is where there is excessive movement due to disruption of the wires connecting the surgically divided sternum. Lack of treatment can result in sternal pain, non-union and infection; factors which may delay the healing of the sternum.[#robicsek-f-fokin-a-cook-j-et-al.-2000,#el-ansary-d-waddington-g-adams-r.-measurement...2007]  This process is shown in the figure below.

Sternal instability is often reported as a ‘clicking/clunking’ sensation in the chest that results in pain and discomfort with activities of daily living (ADL) involving the upper limbs and trunk such as reaching, rolling over in bed and getting up out of a chair.

As sternal non-union and the consequent inflammatory reaction may predispose to mediastinitis or deep sternal wound infection, early detection and management are essential.

Figure 1: Clinical sequence of sternal instability

Risk factors for sternal instability

Risk factors that are thought to contribute to the development of sternal instability and other sternal wound complications include:[#el-ansary-d-waddington-g-adams-r.-relationship...-2007]

• Obesity
• Macromastia (large breasts)
• Large chest circumference
• Smoking history
• Chronic obstructive pulmonary disease (COPD)
• Use of beta-adrenergic agonists
• Diabetes
• Osteoporosis
• Prolonged steroid use
• Inadvertent (off-centre) or repeat sternotomy
• Bilateral internal mammary artery harvesting
• Prolonged mechanical ventilation (> 24 hours)
• Renal failure
• Chronic/persistent cough, secondary to use of type one ACE inhibitors
• Blood transfusions

Sternal assessment

Prior to undertaking a physical assessment, the following should be considered:

• Pain – intermittent/constant, dull/sharp, hot/cold, deep/superficial
• Feeling of instability or excessive motion – e.g., patient reports that their chest 'feels like it is going fall open'
• Sounds – ‘clicking’, ‘clunking’
• Activities that provoke ‘unstable feeling’/pain/clicking/crepitus
• State of wound or scar – including the colour, sensitivity to temperature, discharge (serous or coloured), hypersensitivity, and presence of keloid scarring or adhesions

Physical assessment

The Modified Sternal Instability Scale (see table below) has been shown to have high inter- and intra-rater reliability when used to determine whether the sternum is mechanically stable.[#balachandran-s-lee-a-royse-a-et-al.-2014]

Table 1: Motion grade associated with modified sternal instability

# Special testing may include shoulder flexion (unilateral/bilateral), trunk rotation, lateral flexion, coughing and opposing movements of the upper limb (e.g., flexion, abduction and external rotation of one upper limb accompanied by extension, adduction and internal rotation of the other upper limb).

Assessment method

1. Palpate between the sternal halves using the 2nd, 3rd and 4th digits (as shown in the image below) during:

• Shoulder flexion (unilaterally and/or bilaterally)
• Trunk lateral flexion and/or rotation
• Coughing and deep inspiration/expiration

2. To further challenge the sternum, an additional optional movement is contrary shoulder movement (i.e., one shoulder flexing and externally rotating, while the other shoulder extends and internally rotates).

3. During movement, record grade of motion, bony gap (size) and tenderness.

Figure 2 : Manual sternal assessment during trunk lateral flexion

Frequency of assessment

• Day 5-7 post-cardiac surgery – results should be documented in the medical record and the treating cardiac surgeon should be notified of the assessment outcome should an unstable sternum be detected
• Week 3 – 6 post-surgery
• Prior to commencing exercise – particularly involving upper limb advanced stretches and weight or pulleys (unilateral); should be recorded as an outcome measure on the exercise chart
• On an ongoing basis – when instability is detected and/or following wound infection/breakdown (at 3-4 week intervals)

Sternal precautions

• Bilateral upper limb activity post-sternotomy is recommended. This includes standing from a chair using both arms with equal pressure and use of gait aids that require bilateral upper limb support. Given the low incidence of post-operative pulmonary complications in this population, prophylactic deep breathing and coughing exercises should be used with caution
• A medication review may be necessary for those with a dry, non-productive cough secondary to medications (e.g., ACE inhibitors)
• Movement restrictions should be based on risk gauged by undertaking a sternal instability assessment

Sternal precautions have historically been recommended for all patients who have undergone a median sternotomy in an attempt to avoid excessive shearing and distractive forces at the sternal edges, which would compromise the healing sternum. However, the evidence for this premise has been drawn from expert opinion, institutional protocols and studies on cadaver and replica models.

There is significant variation in the clinical application of sternal precautions amongst institutions, with no consensus on the type and duration of time for which they are applied.[#balachandran-s-lee-a-royse-a-et-al.-2014] Recent studies have indicated that bilateral upper limb movements produce less movement and pain compared with unilateral upper limb elevation, whilst coughing increases movement and pain at the sternal edges.

TIP: Base sternal precautions on an individual’s medical history/risk factors, assessment findings of sternal stability and/or response to exercise as outlined in the sternal precautions algorithm.

Bilateral upper limb activity within patient comfort is advised.

Non-surgical management of sternal instability

For those with established sternal instability, a return to theatre for surgical re-wiring is often necessary. At times, this option is not available if bone quality is poor or confounding risk factors for re-operation exist. Non-surgical approaches involve external bracing and exercises.

1. External bracing (see example below) can be used to: [#el-ansary-d-waddington-g-adams-r.-2008]

• Minimise symptoms
• Provide an interim measure prior to surgical repair
• Prevent the progression of a minimally unstable sternum

Figure 3: “Qualibreath” – an orthopaedic stabilisation brace for a median sternotomy

Reproduced with permission from HjorthHealth, 2012

Specific considerations for women

All women should be encouraged to wear a supportive bra, with wide straps and no underwire, early in the post-operative period to ensure support of their breasts and minimise undue stress on the healing sternum and associated wound. An example of a bra designed specifically for this patient population is the “Qualibra” shown below.

Figure 4:  “Qualibra” – an orthopaedic stabilisation brace for a median sternotomy

Reproduced with permission from HjorthHealth, 2012

2. Exercise prescription and activity

Patients with chronic sternal instability can improve stability and reduce pain by conducting trunk stabilisation exercises for 10 minutes, twice a day over a 6-week period. [#supportive-devices-arch-phys-med-rehabil-2008]

Upper limb exercise prescription

Bilateral upper limb resistance training using weights and pulleys may commence on entry into the outpatient exercise program.

This may include:

• Biceps curls/elbow flexion (biceps/brachialis, coracobrachialis)
• Triceps pull-down/elbow extension (triceps).

Caution: Activities to avoid until the sternum is confirmed as being stable:

• Unloaded extension of the upper limb beyond the plane of the body
• Bilateral resistance training using weights and pulleys that involve abduction or extension of the upper limbs (e.g., pectoral deck)
• Unilateral resistance training using weights and pulleys

Patients who have had a median sternotomy should be provided with education and  Activity guidelines for the sternum following open heart surgery outlining current recommendations for daily activities.

These recommendations are listed below.

Encourage:

• Symmetrical movement for bilateral upper limb activities (e.g., pushing up from a chair)
• Good posture to avoid unilateral stress through the trunk and upper limbs

Avoid:

• Unilateral heavy activities
• Unnecessary driving until advised by the cardiologist/cardiac surgeon

The following activities should be kept to a minimum:

• All activities that involve overhead upper limb activity (i.e., hanging washing, high reaching)
• Pushing large objects (e.g., shopping trolley, lawn mower)
• Carrying weights > 5kgs (e.g., child, shopping bags)
• Heavy manual tasks including housework
• Swimming

The following activities should be avoided if sternal stability is poor:

• Trunk rotation
• Prolonged driving > 1 hour
• Swimming (all strokes)
• Upper limb resistance training

Sternal instability management guide

Sternal instability may be graded on a scale of 0-3 depending on the extent of bony disruption. [#el-ansary-d-waddington-g-adams-r.-trunk...-2007] The table below lists recommendations for the management of patients with sternal instability.

Table 2:  Summary of sternal instability and associated management

Managing sternal stability

• Early and ongoing assessment of the sternum is essential
• Manual assessment is a reliable indicator of sternal instability
• Sternal instability should be reported to the cardiac surgeon
• Activities and exercises should be modified for a patient with sternal instability

Following surgery, movement of the cervical and thoracic spine and shoulders may be reduced in the early post-operative phase. Joint range of motion should be assessed before surgery and throughout the acute post-operative (in hospital) and the post-discharge phases of rehabilitation.

In addition to a walking program, patients should commence thoracic, neck and upper limb exercises whilst in hospital.

The goals of exercise in the 3-4 weeks post-surgery are to:

• Restore range of movement
• Prevent pain
• Prevent deconditioning

Specific mobility exercises of the chest wall should commence at about 3 weeks post-surgery. Thoracic mobility exercises reduce sternal pain at 4 weeks after cardio-thoracic surgery.[#hoggins-tr.-2009]

Examples of patient resources for cervical spine, trunk, and upper limb mobility exercises are provided below. Local protocols established according to current evidence should be adhered to.

• Exercise following heart surgery-the first 4 weeks
• Chest wall mobility following heart surgery-weeks 4 to 12

Patients are often advised to limit upper limb activity following surgery involving a median sternotomy. Protocols vary significantly according to institution and are largely based upon historical guidelines, expert opinion and cadaver studies.

Refer to sternal stability management for more detail.

Implantation of ventricular assist devices (VADs) increase circulating blood flow and allow the patient to undertake exercise at a higher intensity. Maximal intensity, however, is sometimes limited by the device itself. Clinicians prescribing exercise should therefore have a thorough understanding of the physiology imposed by different devices.

Exercise considerations for patients fitted with a VAD include:

• Being prone to post-surgical complications (bleeding, infection, respiratory compromise)
• Often being extremely deconditioned following implantation, but can progress rapidly once post-surgical complications are resolved
• Drive line infections being common and limit some exercises
• VAD hardware (drivers, batteries, drive lines) restricting certain activities, although most activities can be modified to accommodate these. Aquatic activities are not appropriate
• VADs having a system of alarms, some of which require urgent attention. The exercise supervisor should be familiar with their implications for exercise. VAD parameters should be recorded before and after each exercise session and any alarms that are triggered should be documented. In some circumstances, the VAD settings may require alteration, necessitating close liaison with the VAD nurse.

Exercise training is essential to optimise functional ability and fitness prior to transplant surgery, and to accelerate recovery in the post-operative phase. The pre-transplant phase may require shorter duration activities and greater rest periods. Exercise training also helps offset the effects of immunosuppressive medication (muscle atrophy, bone demineralisation, increased adiposity) and assists return to routine life following transplantation.

Patients need to contend with post-surgical complications, episodes of cardiac transplant rejection, altered physiology (cardiac denervation) and infection risk, so exercise should be prescribed and progressed according to individual circumstances and clinical presentation, to enhance continued and prolonged adherence.