Ischaemic cardiovascular disease

Indicator definition

The denominator for this indicator (i.e. what the results are compared against) is the estimated prevalence of ischaemic cardiovascular disease within the PHO population. This is calculated by adjusting the national prevalence of ischaemic cardiovascular disease to the age, gender and ethnicity variables of the PHO population.

This indicator makes up a total of 9% of a PHO’s performance payment (3% for achieving the target in the total population and 6% for achieving the target in the high needs population).*

What is defined as ischaemic cardiovascular disease?

For the purpose of the indicator, ischaemic cardiovascular disease is defined as a medical diagnosis, either current or in the past, of one or more of the following conditions:

• Ischaemic heart disease - acute coronary syndrome, angina, percutaneous coronary intervention (PCI), coronary arterial bypass graft (CABG), myocardial infarction
• Peripheral vascular disease - atherosclerosis, aortic aneurysm
• Cerebrovascular disease - stroke and transient ischaemic attack (TIA)

N.B. Cardiac failure is not included as an indicator due to variable access to diagnostic testing. In addition, not all cardiac failure is caused by ischaemic heart disease.

How should a diagnosis of ischaemic cardiovascular disease be recorded?

The diagnosis of ischaemic cardiovascular disease needs to be recorded in a way that is retrievable. This means that an appropriate read code should be entered on the electronic patient record in the practice management system (PMS).

A G3 Read code detects all coded current and past cases of ischaemic heart disease. A computerised search using G3 automatically captures all lower codes such as G30 for myocardial infarction and G33 for angina. Cardiac procedures such as bypass surgery or angioplasty are listed under Read code 79 (although the patient should also have an existing G3 root code for the condition that required them to undergo the procedure).

A G6 Read code detects all coded current and past cases of cerebrovascular disease, but does not differentiate between atherosclerotic disease and cerebral haemorrhage. A G70-73 Read code detects all coded current and past cases of peripheral vascular disease. In these two cases, specified Read codes are excluded from counting towards the PHO Performance Programme target (Table 2).

The use of the code G70 relates to the Read term atherosclerosis, which in itself provides little clinical context. To record the presence of peripheral vascular disease we suggest the use of the G73z code. This covers the performance programme definition and provides better clinical context for clinicians.

For a list of all Read codes that are identified for the PHO Performance Programme see “Code Mappings for data transfer specification and clinical performance indicator data format standard document.” pages 17-27, available from: www.dhbnz.org.nz/Site/SIG/pho/Technical-Documents.aspx

Any qualifying Read code matched to a qualifying patient will be counted, regardless of when it was recorded. Previously, some PMS’ had an arbitrary ten-year look-back cut-off built into their queries but this limit has now been removed. The PMS error will have adversely affected the levels reported by the PHO Performance Programme prior to April 2011 when the patch was released.

Ways to optimise coding for ischaemic CVD coding within the practice

To decide which approach to ischaemic cardiovascular disease coding is best for your practice, first consider who within the practice might have the skills and time available to review the various sources where information concerning ischaemic CVD can be retrieved.

Sources include:

1. Letters from secondary care, e.g. outpatient clinics, surgical operation notes, inpatient admission letters.
2. Previous medical records (usually in the form of paper-based patient notes), especially from patients that are newly registered with the practice.
3. Audits on medicines that suggest a diagnosis of ischaemic cardiovascular disease such as: anti-anginals (glyceryl trinitrate, isosorbide, nicorandil and perhexiline), dipyridamole and clopidogrel. N.B. Some medicines such as warfarin, aspirin or statins would not be appropriate for this audit as they may be used for conditions others than ischaemic cardiovascular disease, e.g. primary prevention of cardiovascular disease, atrial fibrillation.

Read codes can be added to patient notes within the PMS, at the time of the consultation. When relevant letters from secondary care arrive at the practice, Read codes can be entered directly by the GP reviewing the letter, or by highlighting or underlining any keywords on the letter for another staff member to enter the code.

Check Read codes whenever doing a repeat prescription, and if the code is not there, add it to the list of classifications. When adding a classification it is useful to tick both “long-term” and “add to patient history” on the classifications template in the PMS (if available). This will assist when writing referral letters in the future.

Establish policies within the practice to ensure consistency, accuracy and completeness of disease classification recording and clinical event coding.

Missing medical history?

Some patients have little or no recorded medical history, e.g. they may have immigrated to New Zealand or spent some time out of New Zealand, or their old notes (or parts of their record) may have become “lost” when transferring from one practice to another. When asking these patients about their previous medical history, it may be useful to enquire specifically about whether they have ever had a heart attack, stroke, “mini-stroke” or any heart surgery as these are terms that most people are familiar with.

Also consider opportunistically asking this same question of any patients aged over 50 years, to potentially identify ischaemic cardiovascular disease that is not recorded on the medical record held in primary care.

The main benefit of identifying and coding patients with ischaemic cardiovascular disease is in creating the best opportunity for secondary prevention.

Another important benefit is patient safety - it is easy for other doctors in the practice and locums to know what health problems the patient has when their primary doctor is absent. Accurate coding also ensures that any referral includes this information, which is particularly important if referring the patient for a surgical intervention.

General Practice disease registers - CVD

Consistent coding across general practice enables the development of disease registers. Disease registers group together long-term medical conditions with similar precursor risk factors and secondary preventative measures. Registers can be used to help to plan and organise preventative programmes and appropriate care, monitor the health of the practice population, facilitate audit and review clinical practice.

It is important to understand the difference between disease codes and health event codes. For example, a patient with an inferiolateral myocardial infarct could have the following codes:

The G3 code should be linked to consultations where this specific disease area has been covered. This ensures that the overriding disease class code remains at the top of the classification list in the PMS.