History
A 62-year-old nonsmoking man was referred for upgrade of his dual-chamber pacing system to a cardiac resynchronization therapy (CRT) pacing system. The dual-chamber pacing system had been implanted 4 years earlier. The initial indication for cardiac pacing was complete heart block that developed roughly 8 hours after radiofrequency ablation of the cavotricuspid isthmus for the treatment of symptomatic atrial flutter. The components of this initial pacing system were a St. Jude Medical Victory XL DR 5816, a Medtronic bipolar screw-in atrial lead 5568-53, and a Medtronic bipolar screw-in ventricular lead 4076-58. At the time the initial pacing system was implanted, his left ventricular size and ejection fraction (60%-65%) were normal. On device interrogation he routinely paced more than 99% of the time.
The patient developed fatigue, exercise intolerance, and dyspnea on exertion. After atrial flutter ablation, he was started on flecainide for symptomatic paroxysmal atrial fibrillation. His other pertinent medical history included dyslipidemia and hypertension. His ejection fraction was reassessed. His left ventricular ejection fraction by radionuclide angiogram was 38%. An ischemic cause for his cardiomyopathy was ruled out by elective coronary angiography.
Current Medications
The patient’s daily medications were aspirin 81 mg, cetirizine 10 mg, dutasteride 0.5 mg, enalapril 5 mg, escitalopram 10 mg, flecainide 50 mg, hydrochlorothiazide 25 mg, and simvastatin 80 mg.
Comments
Flecainide is generally avoided in patients with conduction system disease. Flecainide slows conduction that can further widen the QRS complex from baseline, leading for further ventricular dyssynchrony. Flecainide also should be avoided in patients with coronary or structural heart disease because of the increased risk for malignant tachyarrhythmias. Flecainide was discontinued in this patient for these reasons.
Current Symptoms
The patient’s symptoms included fatigue, exercise intolerance, and dyspnea on exertion.
Physical Examination
Laboratory Data
Electrocardiogram
Findings
An electrocardiogram demonstrating atrioventricular sequential dual-chamber pacing at a rate of 60 bpm (Figure 10-1) and QRS duration of 182 ms.
Comments
The morphology of the paced QRS is consistent with a right ventricular apical location. The paced left bundle branch (LBB) morphology suggests right ventricular origin. The predominant positive voltage in lead I is due to right-to-left activation. The apical position is supported by the completely negative morphology in V4 (apical lead) resulting from ventricular activation away from the apex.
Chest Radiograph
Findings
Chest radiography was performed in posteroanterior (Figure 10-2, A) and lateral (Figure 10-2, B) views. The left infraclavicular pacemaker has leads positioned in the right atrial appendage and the right ventricular septum.
Focused Clinical Questions and Discussion Points
Question
What anatomic landmarks are relevant for successful and efficient deployment of a left ventricular lead?
Discussion
A thorough understanding of the coronary venous system anatomy is critical for success with placement of left ventricular leads.4,5 The coronary sinus ostium enters the inferior septal aspect of the right atrium between the tricuspid valve and the inferior vena cava. The fat of the avioventricular groove is typically apparent by fluoroscopy in the right anterior oblique (RAO) view as a landmark to aid in anticipating the location of the coronary sinus ostium. A steerable catheter can be used to engage the coronary sinus ostium, by pulling back the catheter from the right ventricle while torquing it septally (i.e., counterclockwise torque from superior access site). This withdrawal from the right ventricle is observed in the RAO view until the catheter is observed to sway back and forth when the ostium is engaged. At this point the left anterior oblique view can be used to confirm advancement into the coronary venous system within the left heart.1
The relevant components of the coronary venous system include the coronary sinus, great cardiac vein, anterior interventricular vein, middle cardiac vein, and lateral vein(s). A thebesian valve can be present at the coronary sinus ostium. This thebesian valve can present a technical challenge to coronary sinus cannulation that often can be negotiated by entering the inferior margin of the coronary sinus. Blood draining from the inferior interventricular septum returns to the coronary sinus via the middle cardiac vein. The coronary sinus becomes the great cardiac vein. A left ventricular lead in a lateral or posterolateral vein is generally the preferred location for biventricular pacing. The Vieussens valve can be located at the ostium of the posterolateral vein. The Vieussens valve can be obstructive to deployment of a left ventricular lead.3
FIGURE 10-1
An understanding of the coronary venous anatomy and experience with its typical fluoroscopic layout helps avoid complications. The primary complication with implanting a left ventricular lead is dissection of the thin-walled coronary venous system. This can occur with manipulation of the lead and delivery system in the coronary sinus but also with a venogram. Comfort with the anatomy and its typical fluoroscopic layout allows the operator to anticipate how to navigate the coronary venous system and minimize mechanical trauma resulting from misdirection. Other issues that can complicate left ventricular lead implantation include phrenic nerve stimulation and positioning the lead in a nonoptimal location.
Question
How can diaphragmatic and intercostal stimulation be avoided and, if occurring after implant, be nonoperatively assessed and managed?
Discussion
Diaphragmatic and intercostal stimulation should be assessed in nonparalyzed patients before committing to a left ventricular pacing site. This is done by pacing the lead at high output, by visualizing the patient both directly and fluoroscopically, and by feeling the chest wall for diaphragmatic stimulation. This should be done throughout a full respiratory cycle because the stimulation might only transiently depend on relative anatomic positional changes during respiration. Similarly, the intercostal muscles should be palpated for stimulation during high-output pacing. If awake, the patient can be asked if he or she has a hiccups sensation. Despite careful assessment at implant, diaphragmatic and intercostal stimulation can occur after implant. The assessment after implant is similar to that during implant but because the patient is no longer in procedure, different positions of the patient can be checked.
If extracardiac stimulation occurs after implant, attempts to avoid and minimize extracardiac stimulation can be done by programming. Sometimes the left ventricular lead pacing output can be adjusted to a lower setting that no longer produces extracardiac stimulation yet is balanced against sufficient output to effectively and reliably capture. Similarly, unipolar pacing produces a larger area of stimulation than bipolar pacing; thus unipolar pacing is more likely to create extracardiac stimulation. Modern biventricular pacing systems offer multiple programmable pacing vectors that can be used for additional pacing options in the management of issues with capture threshold and extracardiac stimulation.
FIGURE 10-2
Question
What QRS morphology is anticipated with biventricular pacing from the posterolateral vein and right ventricular apex?
Discussion
The QRS morphology of biventricular pacing is anticipated to be a hybrid of the QRS of left ventricular and right ventricular pacing. The locations of the left ventricular and right ventricular pacing leads dictate the QRS morphology based on the myocardial activation patterns emanating from the pacing sites.
A lead in the traditional right ventricular apical septal location produces a QRS that is positive in lead I and has an LBB morphology in lead V1. The apical position leads to a superiorly directed vector and manifests with a QS pattern in the inferior leads (II, III, and aVF). Pacing from a left ventricular lead should produce a QRS with right bundle branch block morphology and a negative QS pattern in lead I (activation from left to right). Pacing from the anterior interventricular vein characteristically has a right bundle branch block (RBBB) morphology with positive deflection in the inferior leads. A negative complex in lead I becomes manifest when pacing from a lateral branch of the anterior interventricular vein.
The QRS morphology of biventricular pacing represents the hybrid of the activation patterns from the right and left ventricular leads. Biventricular pacing via the right ventricular apical and the posterolateral vein produce an atypical RBBB, and the inferior leads manifest biphasic or isoelectric QRS morphology. Activation from the left leads to a negative complex in lead I that also may be isoelectric depending on the balance of activation from the right and left ventricular leads. The QRS duration is generally shorter with biventricular pacing than with single-site pacing. The electrocardiographic manifestation of biventricular pacing has been nicely further detailed in the literature.2
Final Diagnosis
At this point, the working diagnosis was cardiomyopathy suspected to be due to right ventricular pacing for complete atrioventricular block.
Plan of Action
The patient was referred for upgrade of his atrioventricular sequential dual-chamber pacing system to a CRT pacing system with the addition of a left ventricular lead.
Intervention
The patient’s atrioventricular sequential dual-chamber pacing system was upgraded to a CRT-pacemaker system. A Guidant bipolar tined left ventricular lead EASYTRAK 2 IS-1 4543 was deployed, and his generator was exchanged for a Medtronic InSync III 8042.
Extensive fibrosis was noted at the previous generator site. Careful dissection allowed the generator and redundant leads to be freed from the pocket. Intravenous contrast injection demonstrated near total obstruction of the proximal subclavian vein. Despite attempting access from a medial stick, the obstruction was still troubling, so a glide wire was navigated to the inferior vena cava. Serial dilations of the obstruction were made to allow passage of the coronary sinus delivery system. The coronary sinus was cannulated, and multiple potential ventricular venous pacing sites were tested. The pacing thresholds were very high, and a wide QRS morphology occurred with pacing in the posterolateral vein. The QRS morphology was improved when pacing closer to the apex and also at the inferior wall; however, these positions did not appear to be stable. The lead was ultimately placed into an anterolateral branch (as shown in Figure 10-3) with a stable appearance, satisfactory pacing and sensing thresholds, and no extracardiac stimulation at high-output pacing.
Outcome
In clinical follow-up the patient noted symptomatic improvement and his paced QRS duration improved (Figure 10-4) from baseline 182 to 166 ms. The paced QRS morphology is consistent with biventricular pacing via right ventricular apical lead and also a lead within the anterior interventricular vein, as evident on the chest radiograph.
FIGURE 10-3 The new left ventricular lead and generator have been placed. The left ventricular lead appears to be in a satisfactory position, is lateral on the posteroanterior image (A) and appropriately anterior on the lateral image (B), consistent with positioning in the anterior interventricular vein.
FIGURE 10-4 The QRS morphology is consistent with biventricular pacing. V1 demonstrates atypical right bundle branch morphology suggestive of some activation from the left ventricle. Lead I is strongly negative, as would be expected with left to right activation. The inferior leads, however, have a positive vector, as likely from the more superior left ventricular lead position.
Selected References
1. Asirvatham S.J. Cardiac anatomic considerations in pediatric electrophysiology. Indian Pacing Electrophysiol J. 2008;8(suppl. 1):S75–S91.
2. Asirvatham S.J. Electrocardiogram interpretation with biventricular pacing devices. In: Hayes D.L., Wang P.J., Sackner-Bernstein J. et al., et al, eds. Resynchronization and defibrillation for heart failure: a practical approach. Oxford, UK: Blackwell Publishing; 2008.
3. Corcoran S.J., Lawrence C., McGuire M.A. The valve of Vieussens: an important cause of difficulty in advancing catheters into the cardiac veins. J Cardiovasc Electrophysiol. 1999;10:804–808.
4. Habib A., Lachman N. et al. The anatomy of the coronary sinus venous system for the cardiac electrophysiologist. Europace. 2009;11(suppl 5):v15–v21.
5. Stellbrink C., Breithardt O.A., Franke A. et al. Technical considerations in implanting left ventricular pacing leads for cardiac resynchronisation therapy. Eur Heart J Suppl. 2004;6(D):D43–D46.
