Paradoxical pulse: signs, symptoms and causes

2021-08-29 11:22 PM

In a healthy person, the radial pulse decreases in amplitude during deep inspiration. That's because breathing in reduces pressure in the chest, causing more venous blood to return to the right heart. The right ventricle is dilated and the interventricular septum curves toward the left ventricle, preventing blood from returning to the left ventricle

Description

Doctor Adolph Kussmaul first named this symptom in 1873 when he found that there was a mismatch between peripheral pulse loss and inspiratory heart rate response in patients with constrictive pericarditis. Paradox usually means that the heart sounds can be heard but no peripheral pulse is captured.

The definition of a paradoxical pulse is a decrease in systolic blood pressure of more than 10 mmHg during inspiration. This is measured by inflating the cuff above the systolic blood pressure level and noting the peak systolic pressure during expiration. Gradually release the cuff until the examiner hears Korrotkoff during exhalation and inhalation, recording this value. When these two blood pressure values ​​differ by more than 10 mmHg, there is a reverse pulse.

Flowchart of Pulse changes during the normal respiratory cycle

Cause

More popular

Heart compression.

Asthma

Less popular

Extensive pulmonary embolism.

Pressure pneumothorax.

Massive pleural effusion.

Acute myocardial infarction.

Stomach torsion.

Turn off the superior vena cava.

Diaphragm hernia.

Constrictive pericarditis (there is a view that paradoxical pulse is not present in constrictive pericarditis see table “Possible changes-paradoxical pulse and Kussmaul sign in constrictive pericarditis and tamponade” down here).

General mechanism

In a healthy person, the radial pulse decreases in amplitude during deep inspiration. That's because breathing in reduces pressure in the chest, causing more venous blood to return to the right heart. The right ventricle is dilated and the interventricular septum curves toward the left ventricle, preventing blood from returning to the left ventricle. During inspiration, the lungs expand, allowing many pulmonary blood vessels to dilate. Pulmonary stasis with LV obstruction reduces left ventricular stroke volume, thereby reducing peripheral vascularity.

The mechanism of paradoxical circuitry is an exaggeration of this respiratory physiology and, in general, can be caused by the following mechanisms:

Limit the increase in blood flow to the right ventricle and pulmonary artery during inspiration.

There are more blood pools in the pulmonary circulation than usual.

Wide variation in intrathoracic blood pressure during inspiration and expiration - when pulmonary pressure is more negative than left atrial pressure, as a result, blood flows backward from the left atrium into the pulmonary veins during inspiration, thereby reducing the amount of blood for stroke volume.

Prevents venous blood from returning to the left ventricle.

Heart compression

Fluid in the pericardial cavity prevents left ventricular filling but does not prevent right ventricular filling to the same extent. When unequal filling adds to the pulmonary blood pools during inspiration, it exaggerates the reduced normal filling of the left ventricle and the left atrium during inspiration. In this case, the pulmonary venous pressure remains lower than the left atrial pressure, resulting in reduced left ventricular filling as blood is pushed back into the pulmonary vein.

Extensive pulmonary embolism

A large-scale pulmonary embolism causes decreased or lost right ventricular function. Very little blood is pumped out of the right ventricle due to the high pressure in the pulmonary artery. This reduces right ventricular output, along with pulmonary blood pools, and reduces atrioventricular and left ventricular filling, thereby reducing stroke volume.

Respiratory disease

The main mechanism in respiratory disease is thought to be due to wide variations in intrathoracic pressure affecting the aorta and right ventricle.

In the case of airway resistance, or pressure respiration, the negative intrathoracic pressure during inspiration is more than normal, and during expiration, this pressure is higher. The result is an exaggeration of the initial physiological changes.

During inspiration with a resistant airway, an increase in negative intrathoracic pressure causes more blood to flow to the right ventricle and pulmonary artery, reducing blood in the left ventricle, resulting in a decrease in stroke volume.

During expiration, the opposite happens, more blood comes out of the left ventricle, the heart has a larger stroke volume. And so, airway resistance magnifies normal processes, resulting in paradoxical circuitry.

Significance

If evaluated correctly, a paradoxical pulse is an extremely helpful symptom.

In one study, the reverse circuit had a sensitivity of 98% and specificity of 83%, a PLR of 5.9 and an NLR of 0.03. Although there are analyzes showing a sensitivity of 82%, for reasons of less sensitivity and an NLR of 0.03, in the setting of pericardial effusion without paradoxical pulse there is no cardiac tamponade.

In the setting of asthma, a paradoxical pulse is a sign of impending respiratory failure.

Possible abnormalities - paradoxical pulse and Kussmaul sign in constrictive pericarditis and tamponade:

There is a debate regarding the pathophysiology that explains paradoxical pulse and Kussmaul's sign and why one happens and the other doesn't. The traditional view has been that paradoxical pulse occurs in cardiac tamponade and Kussmaul's sign occurs in constrictive pericarditis, and the two signs are mutually exclusive. The reason is as follows:

In constrictive pericarditis, negative intrathoracic pressure during inspiration does not overcome pericardial compression on the atria and ventricles. As a result, during inspiration, normal RV filling does not occur, and the interventricular septum does not extend to the left ventricle (as occurs in paradoxical pulses) and has no effect on stroke volume. left as in cardiac tamponade. In severe pericardial spasms, inspiration does not help return blood to the heart, and it occurs at the same time as increased atrial and right ventricular pressures that inflate the jugular vein, because the heart cannot contain blood from the periphery - Kussmaul's sign.

Constrictive pericarditis = Kussmaul's sign.

Cardiac tamponade = Paradoxical pulse.

Related articles:

Impulse of the artery

The ventricular muscle of the heart: conduction of impulses

Stimulation and conduction of cardiac impulses

Atrioventricular node: slow conduction of impulses from the atria to the ventricles of the heart

Sympathetic and parasympathetic nerves: regulation of rhythm and contraction impulses