USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 52-year-old man comes to the office due to 3 days of progressive dyspnea and purulent sputum production. The patient takes albuterol and tiotropium bromide for moderate chronic obstructive pulmonary disease. His medical history is relevant for a 40 pack-year smoking history, type II diabetes mellitus, hyperlipidemia, and coronary artery stenting 2 years ago. Physical exam shows barrel shaped chest, inspiratory crackles, hepatojugular reflux, pulsus paradoxus, and ventricular gallop. His temperature is 38.1°C (100.5°F), the pulse is 130/min, respirations are 28/min, blood pressure is 130/84 mmHg, and pulse oximetry on room air shows an oxygen saturation of 86%. This patient most likely has which of the following conditions?
Content Reviewers:Rishi Desai, MD, MPH
With cor pulmonale, cor is Latin for heart and pulmonale is Latin for lungs.
Cor pulmonale, then, is a relationship between the two, it’s when a disorder of the lungs causes dysfunction of the heart.
Normally, de-oxygenated venous blood from the body goes into the right atrium of the heart.
From there, it goes into the right ventricle and gets pumped into the lungs where it is reoxygenated as it goes through the pulmonary circulation.
The pulmonary circulation is a low-resistance system with pressures ranging between 10 mmHg and 14 mmHg.
After going through the lungs, oxygenated blood goes into the left atrium, and then into the left ventricle, and finally gets pumped back out to the body.
When the heart can’t pump enough blood to meet the body’s demands, it’s initially called heart dysfunction and can worsen to the point where it’s called heart failure.
This can happen in two ways, either it’s systolic heart failure, where the ventricles can’t pump blood hard enough during systole, or diastolic heart failure, where not enough blood fills the ventricles during diastole, called diastolic heart failure.
Heart failure can affect the right ventricle, the left ventricle, or both ventricles, so someone might have, right-sided heart failure, left-sided heart failure, or both which is called biventricular heart failure.
Cor pulmonale is when a lung disorder causes right-sided heart dysfunction that can develop into right-sided heart failure.
In response, this triggers a process called hypoxic pulmonary vasoconstriction.
Let’s say you have a couple pulmonary arterioles here, meaning they’re in the lungs, and the alveoli of the lungs here, and oxygen exchange between the two.
If one of these alveoli is poorly ventilated, the corresponding arteriole vasoconstricts to divert blood away from it.
This works pretty well, but when lots of alveoli are poorly ventilated like with a lung disorder, they all start to vasoconstrict and the mechanism backfires.
The high pulmonary pressure makes it hard for the right ventricle to pump blood into the pulmonary circulation.
As compared to the left side, the right side of the heart is thinner walled and used to ejecting against a low pulmonary vascular resistance.
In acute lung disorders, like a pulmonary embolism, where a blood clot blocks blood flow in a pulmonary artery, the result is a rapid increase in right ventricular pressure that makes the right ventricle stretch out like a water balloon.