Late Heart Reactions

The heart has a moderate radiation sensitivity and there are numerous late effects that can occur.

Clinical Syndromes

Cardiomyopathy presents with dyspnoea and symptoms of heart failure, depending on severity.
Ischaemic Heart Disease presents with the classical symptoms of angina or myocardial infarction; occasionally these may be silent.
Arrhythmia can present in numerous ways, usually with palpitations and syncope.
Valvular Heart Disease is uncommon but can present with symptoms related to the heart valve involved.
Pericarditis can also present as an early effect. Late pericarditis presents with chest pain, classical ECG changes and dyspnoea.



The myocytes of the heart are relatively resistant to radiation. The endothelium of the capillaries is not; death of endothelial cells leads to fibrosis and nutrient deprivation to surviving cells. The most common form of cardiomyopathy is restrictive due to the increased fibrosis within the myocardium.

Ischaemic Heart Disease

Ischaemic heart disease results from damage to the major coronary vessels. The left anterior descending artery is frequently hit when the left chest wall is treated (for example, with left breast tangents). The damage is similar to the atherosclerosis caused by normal vascular disease and hard to distinguish pathologically.


Arrhythmia occurs with fibrosis of the conducting system of the heart. These changes are due to endothelial damage and stimulation of fibroblasts, leading to poor connectivity between the conducting cells. The most commonly affected region is in the vicinity of the atrioventricular node.

Valvular Heart Disease

Valvular heart disease occurs due to increased generation of collagen within the valve leaflets by stimualted fibroblasts. This is typically a slow process.


Pericarditis following radiation is not well understood, but is likely a combination of vascular damage and ischaemia, with resulting inflammatory infiltrate. Effusions may develop; these need to be examined with cytology to rule out tumour recurrence.

Tolerance Doses

Perez and Brady give the following whole and partial volume tolerance doses, for conventionally fractionated radiotherapy. The clinical endpoint used is pericarditis.

  • Whole Organ
    • TD5/5 of 40 Gy
    • TD50/5 of 50 Gy
  • 2/3rds of Organ
    • TD5/5 of 45 Gy
    • TD50/5 of 55 Gy
  • 1/3rd of Organ
    • TD5/5 of 60 Gy
    • TD50/5 of 70 Gy

Dose Guidelines

The latest QUANTEC data suggest the following dose constraints:

  • Mean dose less than 26 Gy (15% risk of pericarditis)
  • V30 < 46 % (15% risk of pericarditis)
  • V25 < 10 % (< 1 % risk of long term cardiac mortality)
    • This is more relevant for breast treatments where there is only a small amount of heart irradiated.


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