Ba-Dum-Bum Goes Your Heart!

Josh opens by joking about old-fashioned school punishments, including yardsticks, dunce caps, and garlic necklaces. Chuck recalls a second-grade Catholic-school teacher who searched students’ desks during recess, then dumped the messiest desk onto the floor in front of the class and made its owner clean it up before beginning the lesson. He does not remember whether he personally received the treatment, saying the experience may have been traumatic enough to block out. The story ends with Josh noting that he moved to public school in third grade, before they turn to the heart.

Josh and Chuck describe the heart as a hollow, cone-shaped muscle between the lungs and behind the sternum, with roughly two-thirds left of the body’s midline and the apex pointing down and left. It is about fist-sized; the average man’s heart weighs around 10.5 ounces and the average woman’s about 9 ounces. They say heart disease remains the leading cause of death in the United States, with about 2,500 Americans dying daily—one every 34 seconds—while deaths from heart attacks have fallen mainly because emergency treatments have improved, leaving more survivors with chronic heart conditions.

Chuck recommends preventive heart screening beginning around one’s 40s, even for people who feel fit, because plaque can remain hidden until a major event such as a “Widowmaker.” He recalls a college friend who felt strange, drove toward the emergency room, and died in the hospital parking lot. Josh describes undergoing a cardiology workup after feeling occasional somersault-like palpitations and learning that his father’s AFib increased his concern; after two weeks of testing, the cardiologist found nothing wrong. Chuck also had an arterial-calcium scan that was not zero, but lower than his doctor expected.

The hosts explain that the right atrium receives oxygen-poor blood returning from the body, while the right ventricle sends it to the lungs for reoxygenation. Oxygen-rich blood then enters the left atrium, moves into the left ventricle, and is pumped through the body; the left ventricle is the largest and thickest chamber because it must overcome systemic blood pressure. The atria are the incoming chambers and the ventricles outgoing chambers. One-way valves open during contraction and close afterward to prevent backflow. The heart’s three layers are the endocardium, myocardium, and surrounding fluid-filled pericardium.

Using two fists, Chuck illustrates diastole as the relaxed filling phase and contraction as the moment blood moves from atria to ventricles and then out to the lungs or body. The familiar “lub-dub” is not simply the sound of contraction; it comes from the heart valves closing. At rest, the heart beats about 72 times per minute, roughly 100,000 times daily and 38 million times yearly—about 2.5 billion beats by age 70. Babies’ rates peak around 140 beats per minute at three months, then gradually fall toward the adult range of 60–100 because their smaller hearts and higher metabolism require more frequent pumping.

Veins carry depleted blood toward the heart, arteries carry oxygenated blood away, and capillaries connect the two systems. The hosts say arteries have muscular walls, veins rely on valves, and capillaries generally lack their own muscular pumping system. Blood returns through the superior and inferior vena cava, while the aorta distributes blood from the heart. Each beat moves about 70 milliliters—roughly one and a half airplane liquor bottles—amounting to about 1.3 gallons per minute and 1,900 gallons per day. Josh prefers the equivalent of 14,400 miniature bottles daily because it makes the scale easier to imagine.

Specialized pacemaker cells in nodes convert electrolytes such as sodium, potassium, calcium, chlorine, and magnesium into charged ions, producing the electrical wave that makes heart muscle contract and release. Chuck connects this to why electrolytes matter during hydration, although Josh jokes that advertising only made them seem ubiquitous recently. The sinoatrial node normally initiates the rhythm; if it fails, the atrioventricular node or other tissue can take over, though the pulse becomes weaker or less regular. The impulse contracts both atria in about 0.04 seconds, pauses while the ventricles fill, then contracts both ventricles. An EKG records the process as the P wave, QRS complex, and T wave.

The hosts explain that cholesterol, fats, and lipids can build plaque in arteries, producing arteriosclerosis. A partial coronary blockage can cause angina—chest pain from insufficient blood and oxygen—while a complete blockage can cause a heart attack. They distinguish a heart attack, which is a circulation problem, from cardiac arrest, an electrical malfunction in which the heart suddenly stops, and heart failure, a chronic condition in which weakened or stiffened muscle cannot pump effectively. AFib is an irregular rhythm that may have no symptoms but can raise the risks of heart failure, blood clots, and stroke, so family history makes screening worthwhile.

Modern pacemakers, first implanted in 1958 and associated here with Wilson Greatbatch, use a battery and circuitry implanted near the upper chest to correct abnormal rhythms; batteries generally last five to 15 years. Temporary pacemakers can support patients after a heart attack. Artificial hearts go further by replacing the ventricles and connecting through wires to an external driver. The 1982 Jarvik 7 kept Barney Clark alive for about 112 days, although complications around the device—not simply failure of the artificial heart—were fatal; its external power unit weighed as much as a refrigerator. Swedish crime boss Leif Stenberg lived 212 days and argued he was legally dead because Swedish law defined death by a stopped heart.