Negative inotropics in HOCM

[Paramyxovirus]

Hello,
I am a medical student. Can someone please help me to understand how do negative inotropic agents (e.g. b-blockers, nondihydropyridine CCBs, disopyramide) help to reduce left ventricular outlet obstruction in Hypertrophic obstructive cardiomyopathy?

Thanks in advance.

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[francisco84]

Hello,
I am a medical student. Can someone please help me to understand how do negative inotropic agents (e.g. b-blockers, nondihydropyridine CCBs, disopyramide) help to reduce left ventricular outlet obstruction in Hypertrophic obstructive cardiomyopathy?

Thanks in advance.

Think about why HOCM causes an obstruction. Think about what night make that worse

 

[drk]

Those drugs decrease heart rate. Decreased heart rate equals longer duration of diastole. Longer diastole means more time for blood to fill in the heart. More blood in the heart means less obstruction from the structural abnormality. Hence anything that lowers blood in the heart worsens the murmur of HCM and things that increase blood in the heart improve it or lessen it rather.

Also, is it still called HOCM? Considering the majority of patients with this genetic mutation aren't actually obstructive?

 

[Instatewaiter]

Hello,
I am a medical student. Can someone please help me to understand how do negative inotropic agents (e.g. b-blockers, nondihydropyridine CCBs, disopyramide) help to reduce left ventricular outlet obstruction in Hypertrophic obstructive cardiomyopathy?

Thanks in advance.

The decrease LV ejection acceleration and the hydrodynamic forces of the mitral valve (ie the thing that causes the obstruction). In HoCM because of either papillary muscle malposition, excessive pap muscle tissue or these hydrodynamic forces, there is systolic motion of the mitral valve toward the septum creating a dynamic obstruction. Negative inotropes reduce this.

Things that are negatively inotropic without much HR effects (disopyramide) reduce this resting gradient, many argue more than CCB/BB. So negative inotropic agents act independent of their HR lowering effects.

They still call it HoCM. When there is no obstruction they either call it HCM or non-obstructive HCM depending on who you talk to.

 

[Paramyxovirus]

Thank you very much fancisc0, drk and Instatewaiter. I understand it perfectly well now!