**3. The role of extracorporeal membrane oxygenation in the management of acute myocarditis**

Despite its complications, mechanical circulatory support is the most crucial and effective option in the management of fulminant myocarditis refractory to medical treatment providing valuable time for recovery either spontaneously or through the specific treatment described above.

Intra-aortic balloon pump (IABP) is usually the first option acting through afterload reduction and a small increase in cardiac output (around 0.5 L) [20]. Though its complication rate is relatively low compared to more invasive options, IABP cannot support worsening patients exactly due to its limitations of provided flow.

The next option is the percutaneous ventricular assist devices (pLVAD) which consist of Impella and TandemHeart – temporary LVADs implanted through the femoral artery. Their main advantage is the significant increase of cardiac output providing a flow of up to 5 L (depending on which model is used) along with a less invasive approach of surgically implanted VADs. Despite the small series of patients treated with this option, the reported results are generally satisfactory [21]. Their main disadvantages include the support of one ventricle only – usually the left one. As a consequence, this option is limited to patients with adequate right ventricular function to prevent the post-implantation development of right ventricular failure, unless two such devices are implanted simultaneously (one for each ventricle), thus, significantly increasing the odds of adverse effects.

Extracorporeal membrane oxygenation essentially bypasses the heart and provides adequate oxygenation to peripheral organs. Their main use in fulminant myocarditis is as bridge-to-recovery, bridge-to-transplant or bridge-to-bridge (bridge to a more permanent solution such as a durable VAD) in irreversible conditions often as a result of giant cell myocarditis. ECMO efficacy in fulminant myocarditis has been well described with survival rates of around 75% and VAD-free survival rates of around 61% [22, 23].

Even though ECMO supports the peripheral organs, it does not contribute to the unloading of the left ventricle. On the contrary, regardless of central or peripheral configuration, ECMO significantly increases the left ventricular afterload due to the retrograde flow to the aorta. In moderately reduced left ventricular systolic function with peripheral VA ECMO, this results in separate oxygenation of the upper and lower part of the body; the upper body is oxygenated by blood provided by the native flow through the heart while the lower body is oxygenated by blood provided by the device with the "splash" zone lying at some point in the descending aorta [24]. In cases of inadequate lung function, this phenomenon may cause the Harlequin syndrome characterized by hypoxia and cyanosis of the upper body and normal saturation and color of the lower body. The syndrome can be resolved by changing the configuration to a central one whereas the device provides oxygenated blood directly to the ascending aorta. This complication is rare when dealing with fulminant myocarditis due to the generally adequate lung function and the significantly reduced left ventricular function resulting in device blood supply to the whole body since the retrograde flow reaches the ascending aorta.

The above-described increased afterload combined with the significantly reduced ventricular function result in a perpetually loaded left ventricle potentially hindering recovery. In some cases, the aortic valve may remain closed during the cardiac cycle due to the inability of the cardiac muscle fibers to generate enough force/pressure to overcome the increased afterload. This phenomenon is nicely demonstrated by pressure-volume loops (PV loops) (**Figure 3**) which show a significant reduction of stroke volume with increasing ECMO flows. Potential solutions include the concurrent use of IABP, pVADs or direct transaortic left ventricular venting. All of these options provide some amount of left ventricular unloading thus promoting cardiac recovery [25].

Another main ECMO disadvantage is its temporary nature. In general, ECMO support cannot last the past 14 days due to a significant increase in adverse effects with prolonged support. Bleeding due to continuous heparin administration,

*Extracorporeal Membrane Oxygenation for the Support of Adults with Acute Myocarditis DOI: http://dx.doi.org/10.5772/intechopen.109313*

**Figure 3.**

*A simulation showing the unloading potential of IABP, LV venting and Impella in a significantly deteriorated left ventricle supported with ECMO [25]. (The figure is shared through the CC BY 4.0 according to the original article).*

infections and limb ischemia are common in these cases. Specifically for patients with myocarditis, it has been reported that prolonged ECMO support >7 days is associated with a worse prognosis [26]. However, this association could also be explained by the patients' worse clinical conditions resulting to prolonged ECMO support.

Reported predictors of myocarditis patient outcomes supported with ECMO include clinical characteristics, biomarkers and echocardiographic characteristics. The most important clinical predictor is the prolonged prevalence of arrhythmias be they atrioventricular block or ventricular arrhythmias [27]. SOFA score has also been associated with the patient outcome with scores >12 shown to be predictive of death or established heart failure [28]. CK-MB is the most well-reported biomarker with two independent studies agreeing to its prognostic value with levels >95 ng/mL [28] or > 185 IU/L [27] predicting a lower chance of successful weaning. Finally, the only echocardiographic parameter shown to have some prognostic value is the left ventricular posterior wall thickness with better results when >11 mm [27]. Unfortunately, all of the referenced studies are based on a small series due to the low incidence of myocarditis and even lower of its fulminant presentation.

### **4. Conclusion**

Fulminant myocarditis is a rare yet significantly dangerous syndrome that needs urgent referral to tertiary centers for endomyocardial biopsy, advanced heart failure treatments and etiology-specific treatment. Mechanical circulatory support is the cornerstone of its management with extracorporeal membrane oxygenation devices

being the last resort in conditions refractory to medical and less invasive mechanical circulatory support measures. The outcomes with ECMO devices are more than acceptable with a 75% survival rate especially when combined with solutions for adequate left ventricular unloading.
