History
A 69-year-old man had underlying complete heart block and chronic atrial fibrillation, diabetes mellitus, and hypertension. He had a single-chamber pacemaker implanted in 2003 for complete heart block. He developed ventricular tachycardia 8 years previously, which required cardioversion. He was referred for further management.
Current Medications
The patient was taking bisoprolol 5 mg daily, atorvastatin 10 mg daily, perindopril 4 mg daily, warfarin 2 mg daily, and subcutaneous insulin injection. Mixtard 48 units in the morning and 20 units at night.
Current Symptoms
The patient was breathless on moderate exertion.
Physical Examination
Laboratory Data
Electrocardiogram
Findings
Figure 12-1 shows the electrocardiogram (ECG) of the patient before admission to the casualty unit. Figure 12-2 shows the ECG of ventricular tachycardia on admission to the casualty unit.
Catheterization
Findings
The coronary angiogram showed mild coronary artery disease. A plan for conservative management was defined.
Focused Clinical Questions and Discussion Points
Question
What is the anatomic basis of mapping the coronary sinus for location of a phrenic-free stimulation site?
FIGURE 12-1
FIGURE 12-2
Discussion
Anatomic studies have shown that the distance between the left phrenic nerve and the target coronary sinus vein varies between 3.5 and 4.5 mm.3 This variable relationship may be mapped to locate a phrenic-free point using the Medtronic 3830 lead (Medtronic, Minneapolis, Minn.), because the 3830 lead has a tip diameter of 1 mm.
Question
Can the screw tip of the Medtronic 3830 lead reach the myocardium through the coronary sinus wall?
Discussion
Histologic anatomy examination of the coronary sinus veins showed that the distance between the myocardium and the veins at mid and apical regions is approximately 1 to 1.42 mm.1 This characteristic is well suited to the Medtronic 3830 lead because the helical structure, on four to five full turns, is 2.5 mm in length. Therefore the Medtronic 3830 lead needs to be rotated only two to three times to reach the myocardium.
Question
How can engagement of the screw tip be differentiated to be on the myocardial side of the coronary rather than the pericardial side?
FIGURE 12-3
Discussion
If the tip of the lead fixation mechanism engages the pericardial side of the coronary sinus, the pacing impedance will be excessively high, whereas pacing on the myocardial side of the pericardium will yield pacing impedance within the acceptable range.2 Should engagement of the pericardium occur, the lead should be unscrewed and repositioned to another site.
Question
What is the risk for causing pericardial tamponade from multiple fixations within the coronary sinus?
Discussion
The fixation tip of the Medtronic 3830 lead is approximately 1 mm in diameter. Therefore, if the Medtronic 3830 lead must be repositioned, the breach in the coronary sinus wall also should measure 1 mm in diameter. A small breach such as this within a low-pressure system of the coronary sinus will not cause pericardial effusion or tamponade.
Intervention
The patient underwent implantation of a cardiac resynchronization therapy device with a defibrillator. After the coronary sinus venogram was obtained (Figure 12-3), a conventional left ventricular lead was delivered to the target branch. However, pacing using the conventional lead caused phrenic nerve stimulation at different sites within the coronary branch.
FIGURE 12-4
An active fixation lead (SelectSecure 3830, Medtronic) was subsequently delivered into the target branch. Because the 3830 lead has a cable type of design that lacks over-the-wire capability, the lead was delivered to the targeted sites using an inner sheath (Attain Select II Sub-Selection Catheter, Medtronic) in a telescoping fashion.
The SelectSecure 3830 lead was actively secured at the targeted sites by twisting the lead body clockwise two to three rotations. Pacing parameters and lead stability were then tested. In the event the results were unsatisfactory, the lead was repositioned by twisting the lead body counterclockwise for two to three rotations and then actively securing it at another site.
Outcome
The lead was actively secured at five sites within the target coronary sinus branch. The initial two sites caused phrenic nerve stimulation (Figure 12-4, A and B). Failure to capture occurred at the third site (see Figure 12-4, C), and the fourth site had an unacceptably high capture threshold (Figure 12-4, D).
The site where pacing threshold was acceptable with no phrenic nerve stimulation was at the fifth site (see Figure 12-4, D). This spot was located only after careful mapping for its relation to the other site within the same target branch (Figure 12-5, A). The mapping process ensured that the tip of the lead was actively fixed to this spot, thus ensuring the stability of lead at this location (Figure 12-5, B).
FIGURE 12-5
Selected References
1. Anderson S.E., Hill A.J., Iaizzo P.A. Microanatomy of human left ventricular coronary veins. Anat Rec (Hoboken). 2009;292:23–28.
2. Hansky B., Vogt J., Gueldner H. et al. Implantation of active fixation lead in coronary veins for left ventricular stimulation: report of five cases. Pacing Clin Electrophysiol. 2007;30:44–49.
3. Sanchez-Quintana D., Cabrera J.A., Climent V. et al. How close are the phrenic nerves to cardiac structures? Implications for the cardiac interventionalists. J Cardiovasc Electrophysiol. 2005;16:309–313.
