
<b>Heart</b>
 
<b>Irradiation of the left side of the chest puts the heart at risk for early and late effects of radiation</b>. Irradiation of the mediastinum [the central portion of the chest cavity, housing the esophagus, heart, & major blood vessels,] may create a subclinical [unnoticed] cardiomyopathy [damage to the muscle of the heart] in more than one-half of the patients. In addition, irradiation of the mediastinum can make further surgery difficult due to post-irradiation sequelae, and pacemakers can be susceptible to irradiation; consequently, modest radiation doses could induce life-threatening arrhythmias.

<b>The greatest risk for most cancer patients is inadequate treatment of their disease</b>. Although mediastinal radiotherapy is a safer procedure than it was 20 years ago, it still may damage the thoracic viscera, including the heart. Cardiovascular problems tend to present subtly years later, when the patient may not recall the prior radiation or may not deem it significant. Awareness of this long latency period and of the wide spectrum of heart disease that may result from radiotherapy is essential for management of these patients. Radiation-induced pericardial constriction is frequently associated with coronary artery disease, mostly silent, with valvular insufficiency, and with pericardial and myocardial disease. Thorough cardiac evaluation in such patients is mandatory. Surgical treatment frequently uncovers an underlying restrictive myopathy [muscle abnormality] that presents a serious challenge to treat.

<b>Cardiac late effect damage from therapeutic irradiation, can and does cause ischemic heart disease and angina</b>, heart block requiring a pacemaker, heart arrhythmias, pericardial disease including pericardial constriction, heart valve damage [e.g. aortic stenosis, mitral insufficiency] with heart failure, and damage to the heart muscle itself with scarring [e.g. dilated, flabby left ventricle]. Patients often require surgical treatment and postoperative complications are common. 
All of the cardiac damage has a common anatomical denominator: fibrosis [death of tissue, with subsequent scarring], which develops progressively following the radiotherapy. It has now been demonstrated that the incidence of cardiac radiation lesions can be reduced by homogeneous distribution of the dose of radiation administered to the mediastinum, by treating each side alternately, by fractionating the radiation and staggering the sessions and by reducing the cardiac mass which is irradiated.
 
Radiation induced heart disease, with its clinical manifestations, is becoming a growing problem. Its prevalence is increasing, keeping pace with the increased survival of many malignancies. The majority of patients with radiation induced heart disease is constituted by Hodgkin's disease survivors, followed by non Hodgkin's disease, esophageal carcinoma, thymoma, lung cancer, breast cancer and metastatic seminoma. 

Cardiovascular mortality associated with radiation therapy correlates with the dose of radiation to the heart and the amount of the heart that was irradiated. All of the following factors are thus important: laterality of the tumor [left sided irradiation causes more cardiac damage], portal arrangements [shielding, overlap], radiation energy, fractionation, and total dose. The study illustrates that an increased cardiovascular mortality can be avoided by the use of appropriate techniques and avoidance of excessive treatment. 

<b>All patients undergoing chest irradiation require serial cardiac evaluation</b>. Important risk factors of radiation-induced heart disease are previous chemotherapy, total radiation exposure, administration next to the heart and/or on the left side of the chest. The cardiac damage limitation basically is founded on prevention. Significant results have been obtained with fractional exposition, high-energy utilization and "split" zone covering. A comprehensive individual patient risk evaluation will provide a substantial benefit for the future. The consultant cardiologist should cooperate with the oncologist and the radiotherapist, providing specific competence and continuing care.