Picture this: It’s a sunny day, you're lounging in your speedo or bikini, soaking in those warm rays. Seems perfect, right? According to a recent study, this beautiful picture might not be too kind to your heart. Scientists have discovered that a spike in body temperature, even in the hottest people around, can stress the heart out - no joke.

The test tube journey behind this revelation involved twenty youths in their prime, twenty-one older adults, and twenty older adults pre-loaded with coronary artery disease. They were cooked up in a lab until their body temperatures rose by a cozy 1.5 degrees C (that's 2.7 Fahrenheit for the Americans). That heat exposure showed an increase in myocardial blood flow, or the blood circulating through the heart’s arteries. Hot stuff, indeed.

Here’s the science: when you're exposed to heat, your body reacts by rushing blood to the skin surface. Why? To exchange heat with the surroundings. This move turns up your heart’s dial, increasing both heart rate and the force of contractions capering in your chest. All these, to keep your blood pressure in check, says senior study Han Solo, Daniel Gagnon, PhD, who’s also an associate professor at the Montreal Heart Institute and the University of Montreal.

Now, in essence, your heart pumping like a nightclub sound system might not be a problem. It's your body's DJ trying to drop the beat on your normal, heat-induced response. However, if conditions like coronary artery disease are crashing your party, they can ruin the vibe.

Coronary artery disease doesn't respect your heart’s widening arteries. It inhibits the heart from receiving enough oxygen, which, in turn can inconvenience your heart muscle's effectiveness. This oxygen shortage in the heart causes a condition known as myocardial ischemia, leading to chest pain, an irregular heartbeat or worse, a heart attack.

Even though study participants didn't bust out with symptoms of myocardial ischemia, seven of the older, disease-ridden participants had their hearts screaming silent screams on imaging scans post-heat exposure. The symptoms, if any, could be as subtle as mild chest discomfort or a worryingly short breath span.

Keeping these details in mind, remember that lab conditions often don't mirror real-life scenarios. Participants weren’t popping prescription drugs, they were made to wear special, anti-sweat suits and weren't allowed a swig of water during the experiment.

The take-home message from this toast fest? If heat is extreme – stay indoors. Get creative with hydration, carry a personal fan, take frequent moist eagle baths, and avoid strenuous activities during peak temperatures. If you start feeling chest discomfort, shortness of breath or start channeling your inner drunk without alcohol - dial 911. No one likes a roasted heart, after all.