Mitral Valve Regurgitation (MR)
Anesthesia Implications
Anesthesia Implications
Fast, Full, Forward
Fast – Keep heart rate (HR) normal to slightly elevated – reducing HR is not advisable as it would cause increased filling of the left ventricle (LV), which increases the regurgitant volume.
Full – The ventilator should be set to allow sufficient time between breaths for adequate venous return. Intravascular fluid volume should also be maintained/increased to optimize cardiac output
Forward – Decrease systemic vascular resistance (SVR) – Vasodilators such as nitroprusside will improve ventricular function. Increased pressures systemically make it difficult for blood to flow forward, which reduces the ejection fraction and increases the regurgitant volume. In some patients, the reduction in SVR seen with regional anesthesia will be beneficial.
Augment inotropy – maintain or increase inotropy (heart contraction)
Preoperative Screenings – Ask if pt has seen a cardiologist and/or had any cardiac testing. Ask what symptoms the patient has in relation to the condition. Diagnostic values such as ejection fraction, etc and disclosed symptoms like SOB could especially useful when tailoring your approach.
Opioid based anesthetic – when heart function is severely compromised, an opioid-based anesthetic is recommended. In these cases be especially aware of any bradycardia that could be induced by opioids.
The primary idea – Prevent decreased cardiac output. Goal is to reduce regurgitation and improve the forward flow of blood.
Pathophysiology
Also known as Mitral Valve Prolapse
The primary problem here is less blood is propelled forward to the aorta and systemic circulation, but regurgitates backwards into the left atrium. As a result, the left atrium dilates and there is a systemic “back up” which results in pulmonary congestion. Eventually, the back up of blood can lead to more severe pulmonary congestion and right-sided heart failure.
There are many etiologies: Trauma, ischemic heart disease, papillary muscle dysfunction, chordae tendoneae rupture, mitral annular dilation, endocarditis, rheumatoid arthritis, ankylosing spondylitis, carcinoid syndrome, myxomatous degeneration, congenital heart disease, and left ventricular hypertrophy
This is typically identified as a holosystolic murmur which radiates to the left axilla. EKG, Echocardiogram, and chest X-ray will further confirm cause and severity.
The presence and size of a V-wave in the pulmonary artery occlusion pressure waveform correlates directly with the severity of mitral regurgitation.
This condition usually remains “insidious”, or asymptomatic, until left ventricular remodeling and heart failure has gotten severe.
Heart failure in connection with mitral valve prolapse is often due to volume overload of the left ventricle. This causes a “stretching” of the ventricle. You’ll see the books describe this as adding tissue in series – meaning instead of the myocardium thickening/getting stronger, the myocardium grows in diameter and becomes more compliant. This is otherwise called eccentric or dilated cardiomyopathy. The advantage of this initially is that the left ventricle is able to take more volume and the regurgitated quantity remains lower. This is why symptoms can go undetected for several years in patients with chronic mitral insufficiency.
Acute insufficiency, however, will present as pulmonary edema and/or cardiogenic shock.
This condition affects about 2% of the total United States population.
Hines. Stoelting’s anesthesia and co-existing disease. 7th edition. 2018.