The cardiologist has added the cancer patient to his list of concerns. As the list of creative and powerful medications that control and eliminate cancer grows, we have to deal with some unexpected side effects.
The addition of adriamycin (doxorubicin) almost 50 years ago to treat cancer patients was a tremendous advance. Unfortunately, it was soon noted that patients would sometimes develop weak hearts as a side effect. This was largely eliminated by closely monitoring the patients for the onset of heart disease and limiting the total dose of the medication. The discovery that below a certain lifetime dose, the medication was safe permitted the continued use of the medication. More recently new variations of the medication have made it even safer.
In a larger sense, this adventure alerted the medical profession to examine each chemotherapeutic agent for possible side effects on the heart. Fortunately, close attention during drug develop has served to alert oncologists when patients have to be monitored closely to prevent cardiac side effects
The first part of the program is to image the heart before potentially toxic medications are used. This selects out patients who do not have strong hearts and require extra precautions. This is then followed with repeated images at close intervals during therapy and at more distant intervals after the conclusion of therapy. This serves to warn the oncologist to modify the therapeutic strategy if a formerly healthy heart starts to deteriorate.
The monitoring can be done with nuclear scans (MUGA scans) echocardiograms or MRI scans of the heart. MUGA scans are the oldest technique but involve an injection and a dose of radiation. Echocardiograms are the fastest, easiest, rarely require injections and have no harmful radiation. The newest and most accurate technique is the MRI scan. This involves no radiation and is mainly limited by the need for specialized equipment that is not widely available. All of these techniques primarily measure the amount of blood ejected with each heart beat and this called the ejection fraction.
In an effort to develop an early warning system to identify toxic effects before any heart damage is done, a new echocardiographic technique called strain analysis was developed. This looks at the speed of the heart walls themselves and not simply the ejection fraction. This can find very early evidence that the heart is not tolerating the dose of chemotherapy before visible function deteriorates and alert the oncologist to change directions
Presently the majority of chemotherapies do not damage the heart. But cancer patients and their doctors are always looking for newer, better and more powerful therapies. The ability to closely monitor the heart opens the possibility to use more of these stronger therapies and cure patients.
The price of these new powerful medications is an increased degree of vigilance and an expansion of the committee of doctors that care for these patients.
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