We will test the hypothesis that increasing skin wetness, and thus evaporative cooling, will attenuate the increase in core body temperature and accompanying cardiac stress during heat wave conditions in individuals with congestive heart failure. Secondly, we propose that wearing a water-saturated T-shirt will also be beneficial to attenuate the increase in core body temperature and accompanying cardiac stress during heat wave conditions in individuals with congestive heart failure. To accomplish these objectives, individuals with congestive heart failure and otherwise healthy control individuals will be exposed to the simulated heat wave condition (hot and dry) with the following cooling modalities: A) control trial (no limb immersion or skin wetting), B) skin wetting only trial, and C) water-saturated T-shirt trial in a randomized crossover fashion. Thermoregulatory and cardiovascular responses will be evaluated throughout these simulated heat wave exposures.

Primary outcomes variables will be skin and core temperatures, while secondary variables will include measures of cardiovascular stress, myocardial perfusion, heart rate, and echo-based measures of cardiac function.

Inclusion Criteria for healthy control participants:

• Participants must be free of any significant underlying medical problems based upon a detailed medical history and physical exam, and normal resting electrocardiogram. Participants must be 45+ years.

Exclusion Criteria for healthy control participants:

• Known heart disease; other chronic medical conditions requiring regular medical therapy including cancer, diabetes, neurological diseases, and uncontrolled hypertension, lung disease, etc.; as well as serious abnormalities detected on routine screening. Current smokers, as well as individuals who regularly smoked within the past 12 months, will be excluded. Subjects who cannot be age and gender matched to an individual in the heart failure group will be excluded.

Inclusion Criteria for Participants with CHF:

- The participant must have a diagnosis of congestive heart failure (e.g., heart failure with reduced ejection fraction), with the severity categorized as New York Heart Association (NYHA) class II or III. Participants must be 45+ years.

Exclusion Criteria for Participants with CHF:

-Patients who do not have confirmed diagnosis of NYHA class II or III heart failure will be excluded from the clinical group. Potential participants with cancer, diabetes, neurological disease, lung disease, and/or uncontrolled hypertension will be excluded. Potential participants with a left bundle branch block on ECG will be excluded. Patients on anticoagulant therapy will also be excluded. Current smokers, as well as individuals who regularly smoked within the past 12 months, will be excluded. Further exclusions will include severe valvular or congenital heart disease, acute myocarditis, NYHA Class IV heart failure, and/or manifest/provocable ischemic heart disease.