cardiac resynchronization therapy ( crt ) is recommended for patients on optimal medical treatment , suffering from symptomatic chronic heart failure ( hf ) with severely depressed left ventricular ( lv ) ejection fraction ( ef ) ( 35% ) and qrs duration > 120 msec.1)2 ) however , uncertainty remains whether it is beneficial to implant crt devices in patients with severe hf , especially those in cardiogenic shock or end - stage hf , since such patients have been excluded from most crt trials . few cases have been reported about crt implantation in patients with acute decompensated hf being treated with vasopressors / inotropes,3)4)5)6 ) but patients in the intensive care unit requiring mechanical circulatory support were usually not considered as eligible for crt or crt - implantable cardioverter defibrillator ( crt - d )  salvage  therapy . in this report , we present a case of successful extracorporeal membrane oxygenation ( ecmo ) weaning in a cardiogenic shock patient after crt - d implantation . two years prior , she was diagnosed with a rheumatic valvular heart disease with moderate mitral stenosis and mild mitral regurgitation ( mr ) . over the years , her hf symptoms progressed and left ventricular ejection fraction ( lvef ) worsened , despite guideline - directed optimal medical treatment , including angiotensin - converting enzyme inhibitors , diuretics and beta blockers . one year prior to admission , coronary computed tomography angiography was performed to rule out myocardial ischemia ; significant stenosis was not noted . echocardiography showed severe lv dysfunction with an lvef of 25% , and her lv end - diastolic diameter was 72 mm ( fig . the effective regurgitant orifice of the mitral valve was 45 mm , and the regurgitation volume was 43.6 ml . twelve - lead electrocardiogram ( ecg ) revealed atrial fibrillation , left bundle branch block , and prolonged qrs duration of 141 ms ( fig . although high doses of dopamin , and norepinephrine were continuously infused , the blood pressure plummeted to 63/41 mmhg and heart rate ( hr ) was 105 bpm . mechanical circulatory support was started using venoarterial ( va ) ecmo via cannulation of the femoral artery and vein . the patient 's hemodynamic status stabilized with ecmo support having a flow rate of 2.5 - 3.0 l / min . volume overload , dyssynchrony , and increased mr are known to aggravate hf ; ultrafiltration and continuous renal replacement therapy were therefore performed . however , there was no improvement in hemodynamic status even after 8 l of body fluid was removed . echocardiography revealed persistent severe mr and a dilated inferior vena cava with low collapsibility , which are consistent with increased central venous pressure . despite mechanical circulatory support with ecmo for 6 days , tachycardia ( maximum hr rate 150 bpm ) persisted , and ecmo flow was increased to 3.3 l / min . although the ventricular rate reduced to 70 - 80 bpm after amiodarone infusion , the ecmo flow could not be reduced below 2.9 l / min . biventricular pacing with atrioventricular ( av ) node ablation was simultaneously performed while the patient was still under ecmo support , using a quadra assura crt - d device ( st . paul , mn , usa ) . using a 0.14 inch guide wire , a quadripolar lv lead ( quartet lead ; st . paul , mn , usa ) was placed in the lateral branch of the coronary sinus after superselecting the cardiac vein . the selection of coronary vein was performed to enable the longest electrical delay . under fluoroscopic guidance , a single - coil implantable cardioverter defibrillator lead was positioned in the apical septum . we ablated the bundle at the his region , using a 3.5 mm tip deflectable ablation catheter . av block was noted after av node ablation , and complete biventricular capture was achieved . the first lv lead threshold was 2.25 v/0.5 ms and the impedance was 290 ohm ; the right ventricular lead threshold was 0.75 v/0.5 ms and the impedance was 380 ohm . each pacing output was 3.0 v , 2.5 v. biventricular pacing was done over 80 bpm . the lower boundary ventricular tachycardia zone was programmed to 330 ms ( 181 bpm ) , while the ventricular fibrillation zone was set to 270 ms ( 222 bpm ) . lv systolic function recovered , and chamber size decreased , immediately after implantation of the crt device . the inferior vena cava decreased in size with high collapsibility ; however , the amount of mr did not change compared to the previous examination . ecmo weaning was successful , and lv function and chamber size were further improved on predischarge evaluation : qrs duration was 132 msec ( fig . 2b ) , lvef 42% , and lv end - systolic dimension 60 mm ( fig . the patient was discharged under treatment , after prescribing angiotensin ii receptor blocker , diuretics , and beta blockers ; there were no further recurrences of cardiogenic shock or symptoms of hf ( supplementary fig . 1 in the online - only data supplement ) . multiple randomized clinical trials ( rcts ) have shown crt to be an effective treatment for hf patients with reduced ef and increased qrs duration . however , patients with advanced hf being managed with inotropic or percutaneous mechanical circulatory support , and patients with atrial fibrillation , were rarely included in these rcts.1 ) the reasons for exclusion being a high risk of complications and short life expectancy . therefore , the clinical usefulness of crt in these patients remains unclear . there have been few selective studies and case reports investigating the usefulness of  rescue  crt in patients with non - ambulatory new york heart association ( nyha ) functional class iv hf or cardiogenic shock.3)4)5)6)7 ) most attempts , however , have been unsuccessful . for example , in a retrospective study by mantziari et al3 ) 24 patients underwent crt implantation during hospitalization in the cardiac critical care unit . six of these patients supported by an intra - aortic balloon pump were able to be weaned from mechanical circulatory support after crt implantation . two patients did not survive weaning from ecmo after crt implantation.3 ) one pediatric dilated cardiomyopathy case reported weaning from ecmo after crt implantation ; however , intensive care unit treatment was continued due to multiple organ dysfuction.8 ) since our case was categorized as a non - ambulatory nyha functional class iv , it was unclear whether crt would be helpful . broad qrs duration , left bundle branch block,9 ) a nonischemic cause of hf , and significant dyssynchrony confirmed by echocardiography10 ) were favorable factors in this case . thus , we implanted a crt - d . because biventricular pacing is ineffective in patients with atrial fibrillation and intact av conduction due to fast and irregular ventricular response , av node ablation was also performed during crt - d implantation . in general , crt is useful for restoring cardiac synchrony and lv function , and for inducing lv reverse remodeling . the device also helps to reduce lv end - diastolic and end - systolic volume and mr.11 ) the effects of crt gradually appear over several months in most cases . hence , we were unsure whether ecmo could stably support the patient until she recovered . a desirable , early hemodynamic effect of crt immediately after the procedure12 ) can facilitate weaning from pharmacological and mechanical support in end - stage hf.5 ) as expected , echocardiography revealed rapidly improving lv synchrony and contractility after implantation of crt , with stabilization of the blood pressure and hr . crt with av node ablation in an adult patient supported by ecmo due to cardiogenic shock , who was potentially eligible for heart transplantation . controversy remains regarding which patients are the best candidates for  rescue crt. the response of patients undergoing biventricular pacing depends on several factors , including age , sex , underlying heart disease ( cause and severity ) , comorbid illness , type of branch block , qrs duration , degree of dyssynchrony and the presence or absence of atrial fibrillation . as already stated , our patient had favorable characteristics , including broad qrs duration , left bundle branch block , nonischemic cause of hf , and significant dyssynchrony.9)10 ) unfavorable characteristics included atrial fibrillation,13 ) valvular heart disease and ecmo support . crt implantation was performed with the hope that functional mr would improve after resynchronization therapy . consequently , careful decisions regarding whether crt would be beneficial in all critically ill patients , are still at the discretion of the clinician . there have been many reports suggesting that increased hr in patients with hf is associated with an increased risk of mortality and morbidity.14 ) the systolic heart failure treatment with the ivabradine trial ( shift ) was a randomized trial of ivabradine versus placebo , in patients with symptomatic hf associated with reduced ef , sinus rhythm , and a resting hr of 70 bpm or higher.15 ) patients with hr higher than 70 are at increased risk for cardiovascular death and hospital admission for worsening hf.15 ) in our case , the resting hr was maintained at 70 to 90 bpm . however , atrial fibrillation developed rapidly and intermittently , despite optimal medication . in conclusion , our case study suggests that crt with av node ablation could be useful in selecting non - ambulatory nyha functional class iv hf patients supported by ecmo , and the effects of the procedure could facilitate weaning from mechanical support . sbp : systolic blood pressure , dbp : diastolic blood pressure , hr : heart rate , ecmo : extracorporeal membrane oxygenation , crrt : continuous renal replacement therapy , crt - d : cardiac resynchronization therapyimplantable cardioverter defibrillator . apical four - chamber view of transthoracic echocardiography , showing severe left ventricular systolic dysfunction , all - chamber dilatation , and dyssynchronous cardiac motion . apical four - chamber view of transthoracic echocardiography showing improved lv systolic function and lv dilatation dramatically with cardiac resynchronization therapy with defibrillator .
65-year - old woman was admitted to our hospital with acute decompensated heart failure with reduced left ventricular ejection fraction and severe mitral regurgitation . 
 electrocardiography revealed a typical left bundle branch block and atrial fibrillation . 
 her condition deteriorated despite administering high - doses of inotropes and vasopressors . pending a decision to therapy , venoarterial extracorporeal membrane oxygenation ( ecmo ) 
 was performed when the patient underwent a cardiogenic shock . 
 although the hemodynamic status stabilized with ecmo support , weaning the patient from ecmo was not possible . 
 thus , we decided to perform cardiac resynchronization with defibrillator implantation as a  rescue  therapy . 
 five days post - implantation , the patient was successfully weaned from ecmo .