Cancer survivors exposed to anthracycline chemotherapy are at risk for developing cardiomyopathy, which may have delayed clinical manifestation. In a retrospective cross-sectional study, we evaluated the utility of cardiopulmonary exercise testing (CPET) for detecting early cardiac disease in 35 pediatric cancer survivors by examining the associations between peak exercise capacity (measured via percent predicted peak VO2) and resting left ventricular (LV) function on echocardiography and cardiac magnetic resonance imaging (cMRI). We additionally assessed the relationships between LV size on resting echocardiography or cMRI and percent predicted peak VO2 since LV growth arrest can occur in anthracycline-exposed patients prior to changes in LV systolic function. We found reduced exercise capacity in this cohort, with low percent predicted peak VO2 (62%, IQR: [53% – 75%]). While most patients in our pediatric cohort had normal LV systolic function, we observed associations between percent predicted peak VO2 and echocardiographic and cMRI measures of LV size. These findings indicate that CPET may be more sensitive in manifesting early anthracycline-induced cardiomyopathy than echocardiography in pediatric cancer survivors. Our study also highlights the importance of assessing LV size in addition to function in pediatric cancer survivors exposed to anthracyclines.
The development of high-quality research is desired in all healthcare fields. Experimental and nonexperimental designs are used to investigate the effect or association of an intervention and clinical or surrogate outcome. The aims of these methods are to improve knowledge and to develop new strategies to manage a disease or condition. Randomized clinical trials are considered one of the standard methods to test the efficacy of a new drug or intervention; however, they are costly, have reduced generalizability, and cannot be feasible in all scenarios. Well-designed observational studies can provide valuable information regarding exposure factor and the event under investigation. In physical and rehabilitation medicine, where complex procedures and multiple risk factors can be involved in the same disease, the use of observational study must be planned in detail and a priori to avoid overestimations. In this article, we will give an overview of the methods used for observational design studies in physical and rehabilitation medicine using clinical examples to illustrate each method. We will describe when it is appropriate and how to use the observational studies in different scenarios explaining how to deal with potential bias and confounders using the adequate design and statistical plan for the situation.
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