You are provided with a report of an echocardiogram of a patient in the ICU.
INDICATIONS/REASON FOR ECHOCARDIOGRAM:
- Hypotension soon after admission to ICU following prosthetic aortic valve replacement for aortic stenosis . BP 70/30 mm Hg (mean 43 mm Hg). Study performed on adrenalin 10 mcg/min.
LEFT VENTRICULAR EVALUATION
- Small LV cavity size.
- Normal systolic function (EF 60%).
- No regional wall motion abnormalities. E′ = 4 cm/s.
- Moderate to severe concentric LV hypertrophy.
- Flow acceleration noted in LVOT on colour Doppler.
- Mildly enlarged. LA area 26 cm2
- Normal size and systolic function
RIGHT ATRIUM/IVC Normal.
AORTIC ROOT Normal
- Structurally normal mitral valve;
- Systolic anterior motion of the valve leaflets.
- Moderate mitral regurgitation.
- E-wave 0.8 m/s; A-wave 0.5 m/s; Deceleration time 196 ms
- Prosthetic aortic valve is well seated. Trivial paravalvular regurgitation.
- Max vel 5.0 m/s; Mean vel 3.5 m/s;
- Max pressure gradient 100 mm Hg;
- Mean pressure gradient 49 mm Hg
AV: Max vel 5.1 m/s; Mean vel 3.7 m/s;
- Max pressure gradient 104 mm Hg; Mean pressure gradient 55 mm Hg
- Normal tricuspid valve. E-wave 0.3 m/s; Mild regurgitation; TR vel 2.0 m/s
- Normal pulmonic valve
a) What is the cause of this patient’s hypotension? Justify your answer.
b) List 4 principles of management of this patient’s hypotension based on the report. (Abnormal values are shown in bold)
1. What is the cause of this patient’s hypotension? Justify your answer
° Left ventricular outflow tract obstruction.
° Gradient across LVOT and not across valve
2. List 4 principles of management of this patient’s hypotension based on the report.
° Stop adrenalin
° Volume load
° Beta blockers to slow the heart rate and reduce contractility
° Vasoconstrictor without inotropic effect (eg phenylephrine)
Success in answering this question relies on the candidate having sufficient familiarity with TTE reports to be able to rapidly skim through the data, identifying only the abnormal findings.
Armed with a detailed understanding of normal TTE measurements, one can immediately pick up on the systolic anterior motion of the mitral valve leaflets. This feature is present in a few other conditions, but combined with the reported LV hypertrophy one begins to think about dynamic LV outflow tract obstruction. This is confirmed by the LVOT peak pressure gradient of over 100mmHg (whereas anything over 30mmHg is defined as LVOT obstruction).
Now, the cause of the hypotension becmes clear (the patient is on 10mcg/min of adrenaline).
Thus, stopping adrenaline is the first step to recovery of normal cardiac output.
Adequate preload and a nice slow heart rate with decreased contractility is the key. Even with the beta-blockers decreasing contractility, the hypertrophied LV will be able to generate a satisfactory stroke volume - provided it does not block its own outflow tract. The idea is to also increase the duration of diastole for as long as possible. Lastly, a high afterload will likely be required - not only to decrease the LVOT-AV gradient, but to increase the diastolic pressure. A higher than average diastolic pressure will be required to perfuse the subendocardium in a hugely hypertrophied left ventricle. The agents to use in this setting would be phenylephrine, vaasopressin or metaraminol - as they have absolutely no beta-1 inotropic effect.
In summary, the management of HOCM in cardiogenic shock consists of
- Ceasing positive inotropes
- Starting some negative inotropes
- Ensuring a slow rate
- Maintaining a sinus rhythm
- Increasing preload
- Inreasing afterload and diastolic pressure
Walker, Christopher M., et al. "Systolic anterior motion of the mitral valve."Journal of thoracic imaging 27.4 (2012): W87.
Williams, L. K., M. P. Frenneaux, and R. P. Steeds. "Echocardiography in hypertrophic cardiomyopathy diagnosis, prognosis, and role in management."European Journal of Echocardiography 10.8 (2009): iii9-iii14.
Fraser, J., et al. "Dynamic left ventricular outflow tract obstruction in critically ill patients." Critical Care and Resuscitation 4.3 (2002): 170.
Sahoo, Rajendra K., et al. "Perioperative anesthetic management of patients with hypertrophic cardiomyopathy for noncardiac surgery: A case series."Annals of cardiac anaesthesia 13.3 (2010).