The human heart consists of four chambers, including two atria in the upper part of the organ, and two ventricles in the lower half. A muscle called the septum separates the chambers on the right side of the heart from those on the left. Located within a sac called the pericardium, the heart is affected by movement of structures in the body including the lungs. The capacity of the left ventricle is somewhat inhibited during inhalation, as the lungs expand and push on the right ventricle. During a heart beat, blood pressure can drop when a person breathes in; if this effect is more pronounced than normal, it is called pulsus paradoxus.
Systolic blood pressure is typically represented by the top number on a reading. The pulsus paradoxus phenomenon is called so because on a medical exam, the sounds of the heart can be heard even in between pulses. Paradoxic pulse can be used to detect and diagnose various conditions of the heart. It is often assessed along with Kussmaul’s sign, which is the change in shape and pressure of veins that can be caused by pressure on the heart.
When pulsus paradoxus is detected, a physician can further examine a patient in various ways. An examination of the carotid artery as well as peripheral artery pulses is often done. Blood pressure cuffs can also be used to measure the sound of the heart, and waveform analysis is often performed on people with obstructed airways or who are in intensive care. Pulsus paradoxus can be caused by fluid pushing on the heart, a heart attack, a blockage of blood vessels in the lungs, as well as shock to the heart. Other causes can be obesity, a hernia of the diaphragm, or anaphylactic shock.
Bronchial asthma can also cause pulsus paradoxus. Mechanically, the effect may be triggered by an inability for pressure to be properly transmitted through the heart. Blood in the lungs can pool as a person inhales, and if the space around the heart is constricted, the phenomenon is often found as well. Respiratory disturbances associated with asthma can increase the pressure around the heart, affecting how blood is pumped when the heart is constricted by abnormal lung activity.
In various diseases, pulsus paradoxus is expected, but does not always occur if there are defects of the septum or the aorta, which is the main artery leaving the heart. Physicians generally need to look for a combination of things when assessing heart health. The causes of a paradoxic pulse can be determined by assessing the sounds of the heart with a precordial exam, taking an x-ray, or administering an electrocardiogram.