Is it perhaps time for CR professionals to look at current practice of risk stratification and to consider how risky behaviours eg smoking have an indirect effect on risk during exercise corresponding to plaque stability

Paul-Labrador, et al. (1999) proposed that the risk shifts over time, the risk being related to the atherosclerotic plaque stability, and suggests that perhaps our initial risk assessment should be revisited regularly and risk stratification performed at regular intervals in relation to disease stability. Angioplasty patients, for example, are currently considered by many to be low risk, but Paul-Labrador, et al. (1999) found in their survey that this patient group had more complications than the post-MI or bypass patients.

account of the individuals' other health behaviour and motivational risk factors. This is an issue which often leads to confusion, particularly where in primary prevention the focus is on lifestyle issues like smoking and the recognised risk markers for CHD, e.g. hypertension. Box 2.1 poses this question.

The second Canadian Guideline (Stone, et al., 2001) proposal is to use a risk-stratification tool which analyses the risk of subsequent cardiac events (exercise-related) and the risk of disease progression, as directed by the presence and severity of the individual's risk markers. The third Canadian Guideline (Stone, et al., 2001) proposal is to merge the Duke Treadmill score, CCS (Canadian Cardiovascular Society) class score (Campeau, 1976) and the

NYHA (New York Heart Association, 1994) scores. However, although these are three validated tools they have not been validated for use together.

The second Canadian Guideline proposal is worth exploring, as it may give the clinician a more standardised method of risk stratification. It takes the process of risk stratification a stage further, using a scale that generates a score. Additionally, long-term progression risk is taken into account, where the presence and severity of modifiable risk markers are considered. This risk marker score is used in conjunction with the acute risk score giving a quantifiable indication of overall risk.

This would appear to be the first novel approach which attempts to develop a measurable risk-stratification process. In practice, this method would support the approach taken by most CR exercise leaders, where experienced professionals utilise their knowledge, experience and expert judgement to determine both the exercise prescription and appropriate monitoring of individuals within the CR programme. In addition, the approach where other health behaviours are integrated into risk stratification is worth considering. However, the Canadian Association of Cardiac Rehabilitation recently published a second edition of their Guidelines (Stone, et al., 2005). They continue to advocate the use of key principles:

• matching the degree of intervention to the degree of risk;

• recognising that the risk factor burden increases the likelihood of atherosclerotic progression;

• recognising that the likelihood of exercise-related adverse events relates to functional capacity, left ventricular function, ischaemic burden and dys-rhythmic monitoring.

However, they have revised their 1999 proposed system for predicting exercise-related adverse events and acknowledge that programmes encounter logistical problems gaining the required objective information.They have concentrated on determination of functional capacity by use of stress testing as the most practical marker for event prediction.

This serves to highlight the difficulty in establishing a comprehensive, user-friendly model of risk stratification which can be applied by the majority of programmes.

The scenario in Table 2.2 highlights the complexity of implementing risk stratification within the cardiac rehabilitation setting as highlighted by the evidence within this chapter. This individual shows the difficulty of 'ticking a box' in relation to risk stratification and how there is an ever-changing picture that takes into consideration all the factors discussed in the chapter and the use of skilled clinical judgement that informs individualised care packages that offer a menu of services and advice.

Table 2.2. A scenario of a young cardiac rehabilitation patient showing the complexity and changing picture of medical markers, health behaviour and motivational risk factors

Key Characteristics

Time-point 1 (initial event)

• 47-year-old man

• Non-ST elevation MI

• First cardiac event

• Good LV function on echocardiography

• Modified Bruce pre-discharge ETT:

4.6ml.kg-1.min-1 METs limited by chest

pain and max ST depression of -1.75 mm

in anterior leads.

• Pain ongoing after ETT - sent for angiography

Time-point 2 (pre-phase III)

• Returns post-PTCA to single lesion in mid-

LAD

• Asymptomatic

• Stopped smoking

• Completes SWT with estimated MET value of

9.1ml.kg-1.min-1

Time-point 3 (during course of

• Non-compliance with given exercise

phase III)

prescription

• Exceeds target heart rate

• Increases exercise intensity independently

• Unable to use perceived exertion scale as

underestimates own exertion levels

• Demonstrates hostility towards staff who try

to advise re-modification of exercise

behaviour

• Competitive with other patients

Time-point 4 (phase III

• Still lacks self-monitoring skills

completion)

Anxiety and depression scale now indicates

borderline depression

• Altered sleep pattern

• Atypical chest pain

• Recommenced smoking

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