Dynamic left ventricular outflow tract obstruction, often called DLVOTO, is a form of obstructive shock found in critically ill patients, especially those with sepsis. It occurs when the mitral valve leaflet moves forward during systole, known as systolic anterior motion (SAM), and obstructs the pathway for blood to leave the left ventricle. This can happen even when the heart muscle is contracting normally or excessively.

The main reasons this occurs involve a combination of factors: the left ventricle contracting very forcefully, which can be seen in high stress hormone states like sepsis; a small and underfilled left ventricular cavity, often due to low blood volume or widespread blood vessel relaxation; and a high velocity of blood flow through the narrowed outflow tract, which creates a negative pressure that pulls the mitral valve leaflet towards the septum.

Common medical conditions that can cause DLVOTO in critical illness include sepsis, due to its effects on heart muscle function and blood vessel tone; hypovolemic shock resulting from conditions like dehydration or hemorrhage; and the use of strong heart muscle stimulating medications in other types of shock. Other associations include Takotsubo cardiomyopathy and support from a left ventricular assist device.

Patients typically show signs of shock, such as low blood pressure, rapid heart rate, and evidence of poor blood flow to organs. A systolic heart murmur, which may vary with patient position or breathing, can sometimes be heard.

Diagnosis is primarily made using echocardiography. Key findings on imaging include observing the systolic anterior motion of the mitral valve leaflet making contact with the interventricular septum, identifying turbulent blood flow in the left ventricular outflow tract, and measuring a significant pressure gradient across the obstruction. The left ventricle often appears small and hypercontractile.

Treatment focuses on reducing heart muscle contractility, increasing the volume of blood filling the left ventricle, and increasing the resistance against which the heart pumps (afterload). It is important to avoid medications that increase heart muscle stimulation or cause widespread blood vessel relaxation.

Specific medical interventions include cautious administration of intravenous fluids to increase left ventricular volume. Beta-blockers, such as esmolol or metoprolol, are used to slow the heart rate and decrease contractility. Alpha-agonists like phenylephrine or norepinephrine are used to increase afterload, which can help expand the left ventricle and reduce the obstruction. Vasopressin is another option for increasing afterload. Medications that dilate blood vessels, such as nitroglycerin or hydralazine, and strong heart muscle stimulants like dobutamine or high dose epinephrine should generally be avoided as they can worsen the obstruction. Addressing the underlying cause of critical illness, such as treating an infection in sepsis, is also a crucial part of management. When properly identified and treated, dynamic left ventricular outflow tract obstruction is often reversible.

Dynamic left ventricular outflow tract obstruction (LVOTO) is not a condition I learned about during residency, and it is not a condition I have diagnosed regularly, although I have probably missed it many many times. On First10EM, I usually prefer to start with a presenting symptom than a diagnosis, because that is how patients present. […]
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