Heart failure: Pathology review

On the cardiology ward, there were two people who had been admitted to the hospital repeatedly.

The first one is 70 year old Lidia, who had a myocardial infarction about 3 years ago.

She presents with fatigue, and dyspnea.

She says that she usually wakes up at night because of shortness of breath, but using more pillows when sleeping helps relieve it somewhat.

On examination, she has pitting edema in her legs and on auscultation, an S3 sound is heard.

The other person is 81 year old Richard who has been a smoker for the past 50 years.

He is also experiencing fatigue, and has pitting edema, but on further examination, there’s also jugular venous distention and hepatomegaly.

Okay, so, both these individuals suffer from heart failure.

Heart failure is a clinical syndrome used to describe the inability of the heart to pump enough blood or a point at which the heart can’t supply enough blood to meet the body’s demands.

This can happen in two ways, either the heart’s ventricles can’t pump blood hard enough during systole, called systolic heart failure, or not enough blood fills into the ventricles during diastole, called diastolic heart failure.

In both cases, blood backs up into the lungs, causing congestion or fluid buildup, which is why it’s also often known as congestive heart failure, or just CHF.

Alright, first up is systolic heart failure.

One way to think about this is that the heart needs to squeeze out a certain volume of blood each minute, called cardiac output, which can be calculated as the heart rate multiplied by the stroke volume.

The heart rate is pretty intuitive, but the stroke volume is a little tricky.

For example, an adult heart might beat 70 times per minute and the left ventricle might squeeze out 70ml per beat, so 70 x 70 equals a cardiac output of 4900 ml per minute, which is almost 5 liters per minute.