Abstract
OBJECTIVE—To compare the defibrillation efficacy of a novel lead system placed in the middle cardiac vein with a conventional non-thoracotomy lead system. METHODS—In eight pigs (weighing 35-71 kg), an electrode was advanced transvenously to the right ventricular apex (RV), with the proximal electrode in the superior caval vein (SCV). Middle cardiac vein (MCV) angiography was used to delineate the anatomy before a three electrode system (length 2 × 25 mm + 1 × 50 mm) was positioned in the vein. An active housing (AH) electrode was implanted in the left pectoral region. Ventricular fibrillation was induced and biphasic shocks were delivered by an external defibrillator. The defibrillation threshold was measured and the electrode configurations randomised to: RV→AH, RV+MCV→AH, MCV→AH, and RV→SCV+AH. RESULTS—For these configurations, mean (SD) defibrillation thresholds were 27.3 (9.6) J, 11.9 (2.9) J, 15.2 (4.3) J, and 21.8 (9.3) J, respectively. Both electrode configurations incorporating the MCV had defibrillation thresholds that were significantly less than those observed with the RV→AH (p < 0.001) and RV→SCV+AH (p < 0.05) configurations. Necropsy dissection showed that the MCV drained into the coronary sinus at a location close to its orifice (mean distance = 2.7 (2.2) mm). The MCV bifurcated into two main branches that drained the right and left ventricles, the left branch being the dominant vessel in the majority (6/7) of cases. CONCLUSIONS—Placement of specialised defibrillation electrodes within the middle cardiac vein provides more effective defibrillation than a conventional tight ventricular lead. Keywords: ventricular defibrillation; defibrillation threshold; implantable cardioverter defibrillator; middle cardiac vein
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Figure 1 .
Diagrammatic representation of the posterior (caudal) surface of the pig heart illustrating the coronary venous system. The extent of the coronary sinus is shown, together with the relation of the orifice of the middle cardiac vein to the orifice of the coronary sinus. The main trunk of the middle cardiac vein bifurcates into the left and right branches, although occasionally it may trifurcate, with the addition of a middle branch. The azygous vein is a dominant vessel in the pig heart, which drains into the (right) superior caval vein in man. LMCV, left branch of middle cardiac vein; RMCV, right branch of middle cardiac vein.
Figure 2 .
Lateral radiograph of thorax showing the multifilamented middle cardiac vein electrodes in place along with the conventional right ventricular and superior vena caval electrodes.
Figure 3 .
Defibrillation thresholds of different electrode configurations. AH, active housing; DFT, defibrillation threshold; MCV, middle cardiac vein; RV, right ventricular apex; SCV, superior vena cava; T, standard deviation. *p < 0.01 compared with RV→SCV+AH; **p < 0.001 compared with RV→AH.
Figure 4 .
Silicon rubber cast (A) showing a short middle cardiac vein and the close proximity of its orifice to the orifice of the coronary sinus (*). The border regions of the coronary sinus are marked by a dotted line. A two chamber apical view (B) shows that the main branch of the middle cardiac vein reaches the musculature of the interventricular septum (IVS) in a high position. AZV, azygous vein; GCV, great cardiac vein; LV, left ventricle; marg veins, marginal veins; MCV, middle cardiac vein; RV, right ventricle; TV, septal leaflet of tricuspid valve. Length of scale bars, 15 mm (A) and 6 mm (B).
Figure 5 .
Silicon rubber cast (A) and two chamber apical view (B) showing bifurcation of right and left branches from the main trunk of the middle cardiac vein (MCV). The borders of the coronary sinus are shown by the dotted line. The left branch of the MCV (LMCV) anastomoses with the marginal vein (marg vein) close to the apical musculature. The right branch of the MCV (RMCV) reaches the musculature of the interventricular septum (IVS) in a distal position. AZV, azygous vein; GCV, great cardiac vein; LV, left ventricle; RV, right ventricle. Length of scale bar, 10 mm.
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
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