Abstract
1. Electrical causes of cardiac dysfunction include absence of AV synchrony, dyssynchronous ventricular activation, and tachycardia-induced cardiomyopathy.
2. Each of these three factors should be considered in any patient with severe ventricular dysfunction and every effort undertaken to eliminate them. Elimination or reduction of tachyarrhythmia burden (using drugs, ablation, surgery, and or antitachycardia pacing), reducing dyssynchrony (by elimination of ventricular pacing or appropriate resynchronization therapy), and providing AV synchrony by placement of appropriate leads are all important in the management.
3. Transplant can be delayed, or even avoided, by the abovementioned measures in select patients.
Final diagnosis: Pacing-induced cardiomyopathy
Interventions:
Tachyarrhythmias were controlled with a combination of amiodarone and flecainide.
The patient was taken to the electrophysiology laboratory for electroanatomical mapping of the right atrium. The baseline rhythm was noted to be junctional at a rate of 60 beats/minute. The intrinsic QRS duration was 176 ms. High-density voltage mapping of the right atrium demonstrated diffuse scarring, but with a small region of viable myocardium, with p wave of 0.8-1.3 mV and acceptable pacing threshold ( Figure 2 ). The implantable cardioverter-defibrillator generator was removed and the electroanatomical map was used to guide a new pacing lead (St Jude Tendril STS, 46 cm; St Jude Medical, St Paul, MN, USA) to this location.
The following hemodynamics were recorded during the procedure:
Condition #1 (atrial pacing 90 beats/minute) Cardiac output 3.10 liters/minute, cardiac index 1.78 liters/minute/m2ÐA pressure: 40/24/30 mm Hg, wedge pressure: 24 mm Hg
Condition #2 (junctional rhythm) Cardiac output 2.65 liters/minute, cardiac index 1.64 liters/minute/m2ÐA pressure: 53/20/30 mm Hg, wedge pressure: 23 mm Hg
Outcome: The patient improved with AAI pacing. He was discharged from the hospital with milrinone. Within 3 months, his ventricular function demonstrated improvement by echocardiography. Within 6 months, he was weaned off milrinone.
Keywords
Atrial tachycardia, Cardiac resynchronization therapy, Pacemaker, Sinus node dysfunction, Tetralogy of Fallot
History
The patient was born with tetralogy of Fallot and underwent complete repair with transannular patch and ventricular septal defect closure in infancy. By age 16 he had developed progressive right heart dilation and severe tricuspid regurgitation. He underwent pulmonary valve placement, tricuspid valvuloplasty, and right atrial plication.
Six months later, at age 17, he presented with supraventricular tachycardia. He was taken to the electrophysiology laboratory for evaluation. The tachycardia cycle length was 340 ms with 2:1 atrioventricular conduction. The P wave morphology was thought to be consistent with either an atrial tachycardia or atypical atrial flutter. Radiofrequency lesions were delivered to create a line of block from the superior vena cava to the midposterior free wall of the right atrium, as well as from the tricuspid valve to the inferior vena cava. After lesion delivery, the tachycardia could still be induced with isoproterenol administration. The area of earliest atrial activation was then located at the coronary sinus ostium, and ablation was undertaken there. The tachycardia was terminated and was not inducible thereafter.
Four months later, the patient presented to the emergency room with a heart rate of 160 beats/min. Cardioversion was performed with a 50 J synchronized shock, with conversion to sinus rhythm. Unfortunately, the tachyarrhythmia recurred 2 h later. Repeat electrophysiology study and catheter ablation were then performed. An intraatrial reentrant tachycardia circuit was found to involve the isthmus between the right atriotomy and tricuspid valve. It was successfully ablated, along with two other tachycardia foci.
Over the next 2 months, the patient was admitted twice for symptomatic tachyarrhythmia. For both, direct current cardioversion was attempted but was unsuccessful. A 12 lead electrocardiogram from that time revealed atrial flutter with a ventricular rate of 120 beats/min, complete right bundle branch block, and QRS duration of 170 milliseconds. An echocardiogram demonstrated mildly to moderately diminished left ventricular systolic function, which had worsened since the previous month.
Soon after, at age 18, he was taken back to the operating room for a redo sternotomy, tricuspid valve replacement with 29 mm Mosaic porcine valve, modified Maze procedure, and biventricular implantable cardioverter-defibrillator (ICD) (St Jude Unify Assura CRT-D; St Jude Medical, St Paul, MN, USA). Eight cryolesions were delivered within the right atrium during the Maze procedure. A right atrial pacemaker lead implant was then attempted in numerous endocardial and epicardial locations. Reliable atrial sensing and pacing could not be achieved, a difficulty attributed to the MAZE procedure, but a bipolar lead was placed transmurally into the atrial myocardium (St Jude Tendril STS, 46 cm; St Jude Medical, St Paul, MN, USA). Likewise, an epicardial bipolar lead (Enpath Myopore Sutureless Myocardial Pacing Lead, 35 cm; Enpath Medical, Minneapolis, MN, USA) was placed with one electrode on the right ventricular free wall and the other electrode on the left ventricle for biventricular pacing. A subcutaneous defibrillation coil (Medtronic Subcutaneous Lead System, 41 cm; Medtronic, Minneapolis, MN) was then implanted along the posterior pericardium. After the operation, the patient was in junctional rhythm. Transesophageal echocardiogram demonstrated severely diminished biventricular function and moderate-to-severe tricuspid insufficiency.
The atrial tachyarrhythmia quickly recurred and his condition worsened over the next month. He re-presented to the hospital with lightheadedness, nausea, and chest pain. Cardioversion was unsuccessful with 100, 150, and 200 J synchronized energy. He was started on amiodarone and milrinone infusions. His tachyarrhythmia improved with amiodarone, but the left ventricular ejection fraction had deteriorated to 20%.
He was transferred to our facility for consideration of orthotopic heart transplantation. Device interrogation revealed a nonfunctioning atrial lead but otherwise normal device function and lead characteristics. The pacing mode was set to VVI with a lower rate of 70 beats/min. The underlying rhythm was junctional and poorly tolerated.
Physical Examination
104 BP/65 mmHg, HR 81 bpm, oxygen saturation 97% on 2 L via nasal cannula.
Weight 65.5 kg
Appearance: The patient appeared comfortable with normal work of breathing.
Neck veins: Jugular veins were distended.
Lungs/chest: Crackles were appreciated at the left base. Otherwise aeration was normal.
Heart: The rhythm was irregular. S1 and S2 were appreciated. A grade II/VI systolic ejection murmur was appreciated at the left upper sternal border.
Abdomen: The abdomen was normal with no ascites or organomegaly.
Extremities: The extremities were warm without edema.
Skin: Midline sternotomy and left upper chest incisions were clean, dry, and intact.
Laboratory Data (Obtained Prior to Transfer)
Hemoglobin 10.3 g/dL
Hematocrit 31%
Middle cardiac vein 87 fL
Platelet count 304 × 10 9 /L
Sodium 134 mmol/L
Potassium 3.5 mmol/L
Creatinine 0.7 mg/dL
Blood urea nitrogen 10 mmol/L
Brain natriuretic peptide 369 pg/mL
Troponin I 0.09 ng/mL
Lactate 0.7 mmol/L
