Ischaemic heart disease (K74/K75/K76)

March 3, 2023
Clinical course of ischaemic heart disease

Ischaemic heart disease may manifest as asymptomatic coronary atherosclerosis, as (stable) angina pectoris and / or as acute coronary syndrome (ACS). ACS comprises instable angina pectoris (IAP) or acute myocardial infarction (AMI).

Angina pectoris (AP) refers to chest symptoms from myocardial ischaemia. Stable AP is characterised by chest tightness or pain, is provoked by physical exercise, emotions or cold, and disappears at rest or with sublingual nitrates within 15 minutes.

In ACS, symptoms are generally more severe and rest or nitrates do not completely resolve the symptoms. In IAP, myocardial ischaemia occurs progressively at rest or at minimal physical exertion.

In AMI, myocardial necrosis occurs, resulting in biochemical markers of myocardial damage. At least one of the following items is also present: clinical signs of AMI (sudden chest pain or tightness), corresponding abnormalities on the electrocardiogram or at coronary imaging or an identified thrombus in coronary angiography or autopsy.

The most common symptom of ischaemic heart disease in both men and women is chest pain. The pain sometimes radiates to the left arm or shoulder. Other common symptoms are dyspnoea or difficulty breathing. Transpiration, pallor and nausea or vomiting may also occur, especially in ACS. Less common symptoms are interscapular pain, dizziness, neck pain, palpitations, pain in the right arm, shoulder or jaw, dyspepsia, epigastric pain and fatigue. Patients may be anxious or agitated. There is a large variety in the presentation of signs and symptoms, making clinical diagnosis challenging.

If stable AP is suspected, cardiovascular risk factors should be assessed and the patient should be referred to the cardiologist to confirm or reject the diagnosis. Treatment consists of symptom control (nitrates, beta-blockers) and secondary cardiovascular prevention (lifestyle, platelet aggregation inhibitors, statins, blood pressure management).

In patients suspected of having ACS, an urgent referral with ambulance transport is indicated. While waiting for emergency transport, nitrates, fentanyl or morphine may be administered, along with oxygen and platelet aggregation inhibitors.

In hospital, treatment is started to restore oxygen supply to the heart (e.g. percutaneous coronary intervention). Cardiovascular risk management is then initiated.

How is ischaemic heart disease recorded in FaMe-Net?

Three ICPC-codes are used: K74 for episodes relating to ischaemic heart disease with angina pectoris (i.e. symptomatic ischaemia); K75 for myocardial infarction; K76 for ischaemic heart disease without angina (asymptomatic). Based on the ICPC-classification, it is not possible to differentiate between IAP and AP. It has been agreed in FaMe-Net to additionally record K74 or K76 in patients who have had a myocardial infarction (depending on the presence / absence of angina). This means that care related to the treatment and immediate aftermath of an AMI is coded under K75, and subsequent CVRM actions are coded under K74 or K76.

On this website, it is not possible to determine the co-occurrence of several ICPC codes within the same person. This would be possible with additional data extractions (upon request).

Different symptom diagnoses are used to code symptoms in cases when ischaemic heart disease cannot be diagnosed but symptoms that could fit it occur. Heart pain (pain attributed to the heart) is coded K01. Pressure / tightness attributed to the heart is coded K02.

Chest pain ‘not otherwise specified’ is coded A11.

Chest symptoms / complaints (attributed to the musculoskeletal system) are coded L04.

Epidemiology of ischaemic heart disease in FaMe-Net

Acute myocardial infarction has an incidence of 0.9 per 1000 patient years, meaning one new diagnosis of AMI among 1000 patients in a year. The incidence among men (1.3) is two to three times higher than that among women (0.5 per 1000 patient years). There is a marked increase in incidence with age, which starts earlier in men than in women. At older ages, the sex difference in incidence decreases. This is a well-described phenomenon. Link/Figure 1

The incidence of ischaemic heart disease with angina (K74) is 0.8 per 1000 patient years. Link/Figure 2 Some (not all) of these new diagnoses of ischaemic heart disease with angina involve acute coronary syndrome, but it is not possible to determine exactly which part this is, as the code K74 is used not only for acute (ACS) but also for non-acute ischaemia (stable AP), as well as for CVRM registration.

The incidence of ischaemic heart disease without angina (K76) is 0.9 per 1000 patient years Link/Figure 3

The prevalence of ischaemic heart disease with angina (K74) is 12.8 per 1000 patient years, meaning that out of 1000 patients in a year, 13 contact their GP for care registered with K74 (i.e. either with clinical signs / symptoms of ischaemic heart disease with angina or for CVRM). Link/Figure 4

The prevalence of AMI (K75) is 8.9 per 1000 patient years. Link/Figure 5

The prevalence of ischaemic heart disease without angina (K76) is 8.1 per 1000 patient years. Link/Figure 6

The symptom diagnoses heart pain (K01) and pressure / tightness of heart (K02) have an incidence of 2.2 and 1.5 per 1000 patient years, respectively. Link/Figure 7, Link/Figure 8 Chest pain NOS (A11) and (musculoskeletal) chest symptoms (L14) have an incidence of 3.8 and 18.7 per 1000 patient years, respectively. Link/Figure 9, Link/Figure 10

The prevalence of heart pain (K01) and of pressure / tightness of heart (K02) is 3.7 and 2.8 per 1000 patient years, respectively. Link/Figure 11, Link/Figure 12

The prevalence of chest pain NOS (A11) and of (musculoskeletal) chest symptoms (L04) is 5.1 and 21.9 per 1000 patient years, respectively. Link/Figure 13, Link/Figure 14

Which initial RFEs do patients with ischaemic heart disease present to their GP?

The most common initial reason for encounter (RFE) for acute myocardial infarction (K75) is an administrative procedure (*62), which occurs in 22% of all episodes, meaning that the diagnosis is reported to the GP in a (specialist) letter. This implies that the GP had no role in diagnosis and initial management (e.g. because an ambulance was called immediately or the patient was already in hospital).

Importantly, a substantial number of episodes of AMI (K75) lack an initial RFE. A manual search shows that episodes without an initial RFE started with a letter (without registration of RFE *62). This means that the proportion of episodes of AMI starting without GP involvement is much higher. The dataset contains n=234 new episodes of AMI, while only n=158 initial RFEs were recorded. Missing RFEs (at least n=76) account for 32% of all episodes. Presented RFEs are calculated as percentages of the registered RFEs (n=158).

The RFE ‘initiated by healthcare provider’ (*64, in 8%) indicates that the GP heard of the AMI through a specialist letter, family, or otherwise, and then contacted the patient. The most common symptom presented to the GP is heart pain (K01), recorded in 13%, followed by pressure / tightness of heart (K02) in 8% of episodes and shortness of breath (R02) in 7%. In 6% of all episodes of AMI, the patient stated in the beginning of the consultation that they thought they were having a myocardial infarction (K75). Link/Table 15

Pressure / tightness of heart (K02) is more common in the oldest (75+) patients with AMI than in younger patients, and is the most common initial symptom in this age group. Link/Table 16 It is also a more common symptom in women (13%) than in men (6%) with AMI. Link/Table 17, Link/Table 18

Although caution is needed because of the very small absolute numbers, it is interesting to note that of all episodes starting with RFE AMI (K75), i.e. episodes in which the patient starts by saying he thinks he has an infarction, in 71% of cases the final diagnosis indeed turned out to be an AMI. Link/Table 19

The three most common RFEs for episodes of ischaemic heart disease with angina (K74) are similar to those for episodes of AMI (K75): administrative procedure (*62), heart pain (K01) and pressure / tightness of heart (K02). Link/Table 20

Episodes of ischaemic heart disease without angina (K76) usually do not start with symptoms but with an administrative procedure (*62), as a ‘check’ (*31) or when ‘initiated by GP’ (*64). This reflects that these episodes are used for registration of cardiovascular risk management after an ischaemic event, or as an abnormal finding in investigations of individuals without typical AP symptoms. Link/Table 21

How do FaMe-Net GPs act?

The most common GP intervention coded for AMI (K75) is prescription of medication which occurs in 80% of episodes per year. Blood tests occur in 16%. Link/Table 22 In only 6% of episodes that turned out to be AMI (K75) the GP refers to a medical specialist, usually (in 5%) the cardiologist. Link/Table 23 This percentage seems very low, but note that all percentages are calculated per calendar year (not per unique episode), and that episodes of AMI (K75) are apparently recorded as episodes of chronic care anyway (given the high prevalence compared with incidence, i.e. 8.9 and 0.9 per 1000 patient years, respectively). It seems that a (re)referral is not often needed in this chronic phase. Moreover, we found that an AMI often occurs without initial GP interference, so no referral is recorded in the acute moment. Primary care referrals occur occasionally, mainly to physical therapy. Link/Table 24

Interventions for ischaemic heart disease with angina (K74) are similar to those for episodes of AMI, with 9% annual referrals to specialists and similar prescription rates. Blood tests reflecting CVRM occur in 25% of episodes. Link/Table 25 For ischaemic heart disease without angina (K76), blood tests occur in 29% per year. Link/Table 26