1074 JACC Vol. 14, No. 4 October 1989: 1074-83 Pericardiocentesis Guided by a Pulse Generator JAMES S. TWEDDELL, MD, ARIAEN N. E. ZIMMERMAN, MD, PHD, CONSTANCE M. STONE, MD, CHRIS K. ROKKAS, MD, RICHARD B. SCHUESSLER, PHD, JOHN P. BOINEAU, MD, FACC, JAMES L. COX, MD, FACC St. Louis, Missouri This study was performed to compare pericardiocentesis strengths. The pacing studies were performed both with guided by a pacing current applied through the pericardio- and without a hemodynamically significant pericardial ef- centesis needle with the traditional method of monitoring fusion to determine if increased pericardial pressure altered ST segment elevation from the needle tip electrogram. ST the pacing threshold. A 4 mA unipolar cathodal stimulus segment elevation was measured at 3 mm from the epicar- was chosen because it captured the ventricle only with dium, after epicardial contact, after epicardial penetration direct contact of the epicardium. Ten dogs were instru- and again at 3 mm from the epicardium after epicardial mented and cardiac tamponade produced so that a subxiph- penetration. Two millivolts of ST segment elevation gave oid approach to the epicardium with the pacing needle the highest combined positive (86%) and negative (79%) electrode could be attempted. During pericardiocentesis, predictive value for epicardial contact by the pericardio- needle tip electrograms were recorded, alternating with centesis needle between the two groups with the largest pacing attempts using a 4 mA unipolar stimulus. In all 10 difference: 3 mm from the epicardium before contact and dogs, the effusion was entered and epicardium was con- after epicardial penetration. Therefore, ST segment moni- tacted as indicated by capture. No myocardial perforation toring cannot reliably determine the point of epicardial or coronary artery or venous injuries were produced. These contact. findings support the use of a pulse generator to guide To determine the optimal stimulus strength for pulse pericardiocentesis. generator-guided pericardiocentesis, pacing studies were (J Am Co11Cardiol1989;14:1074-83) performed using 2, 4, 6, 8 and 10 mA unipolar stimulus The diagnosis of cardiac tamponade is suggested by the myocardial injury (1,2). Echocardiography is often not im- findings of hypotension, increased central venous pressure, mediately available to assist in pericardiocentesis in a patient pulsus paradoxus, loss of the apical impulse, and distant who may already be near death. Bishop et al. (3) initially heart sounds. Any of these signs, except hypotension, may described the use of the electrocardiogram (ECG) as a be absent or altered by coexisting injuries, myocardial safeguard in pericardiocentesis. The pericardiocentesis nee- disease or thoracic disease. The ability to diagnose quickly dle is connected to the precordial lead of the ECG, and ST and drain a pericardial tamponade or to rule out this cause of segment elevation is monitored as an indicator of epicardial hypotension so that another may be sought would greatly contact. However, ST segments can be altered by medica- benefit the management of this group of patients. Pericardio- tions, pericarditis, ventricular hypertrophy, ischemia and centesis is performed most safely with the aid of cardiac infarction, thus limiting the usefulness of ECG monitoring as ultrasound to confirm the diagnosis and avoid inadvertent a safeguard. Negative findings on pericardiocentesis do not indicate absence of an effusion (4-6). A simple technique to localize the tip of the pericardio- From the Department of Surgery, Division of Cardiothoracic Surgery, centesis needle to the epicardium, and therefore within the Washington University School of Medicine, St. Louis, Missouri. This study pericardial space, could improve the yield of pericardiocen- was supported by Grants ROl HL32257and ROI HL33722from the National Institutes of Health, Bethesda, Maryland. tesis. In addition, if the point of the epicardial contact could Manuscript received December 5, 1988; revised manuscript received be determined precisely, myocardial injury could be March 2, 1989,accepted April 7. 1989. avoided. Our objective in this study was to show that, by Address for reorint$: James L. Cox, MD, Division of Cardiothoracic Surgery, 3108 Queeny Tower, Box 8109. 4989 Barnes Hospital Plaza, St. applying a pacing current through the pericardiocentesis Louis, Missouri 63110. needle, the moment of epicardial contact could be reliably 01989 by the American College of Cardiology 0735-1097/89/$3.50 JACC Vol. 14. No. 4 TWEDDELL ET AL. 1075 October 19X9: 107&G PULSE GENERATOR-GUIDED PERICARDIOCENTESIS The needle stabilizer consisted of a rectangular base, 1.5 X 2 cm with a 1 cm diameter hole, which allowed it to be sutured with four 4-Osilk sutures to the surface of the heart. The base was connected to two struts, 2 cm tall, that supported a rubber diaphragm. The pacing needle electrode was introduced through the rubber diaphragm and directed toward the exposed epicardium in the base. The rubber diaphragm supported the pacing needle electrode and held it at any chosen distance from the heart. Study Design This study was performed in four groups of dogs. All experiments were performed in anesthetized mongrel dogs of either gender weighing 25 to 35 kg. All animals received need1 humane care in compliance with the “Principles of Labora- tory Animal Care” formulated by the National Society of Medical Research and the “Guide for the Care and Use of Laboratory Animals” prepared by the National Academy of Sciences (National Institutes of Health publication No. 80-23, revised 1978). Group I: open chest cardiac electrograms recorded with Figure 1. Pacing needle electrode and needle stabilizer. The pacing needle electrode for closed chest studies (A) consisted of an 18 or 20 use of the precordial lead of the ECG. To determine the gauge spinal needle insulated along the length of the barrel with degree of ST segment elevation that signaled epicardial Teflon. The hub was soldered to a multistranded stainless steel- contact or epicardial injury compared with that recorded at a insulated wire. For open chest studies (B), the pacing needle small distance from the epicardium, we recorded an electro- electrode was modified by grinding off the bevel of the needle so that gram using the ECG set to record a precordial lead at a the tip was blunt. The needle stabilizer(C) consisted of a rectangular base I.5 x 2 cm with a 1 cm diameter hole, connected to two struts. distance of 3 mm from the heart, after contact with the 2 cm tall, that supported a rubber diaphragm. The pacing needle epicardial surface, and after intentional epicardial penetra- electrode was introduced through the rubber diaphragm, which tion injury and at a distance of 3 mm from the heart supported the pacing needle electrode and held it at any chosen immediately after epicardial penetration. Six dogs were distance from the heart. anesthetized with pentobarbital (30 mg/kg body weight), intubated and ventilated with a Harvard respirator. A right fifth interspace thoracotomy or median sternotomy incision determined because it coincided with capture of the ventri- was used to enter the chest. The pericardium was arranged cle, and that this procedure could increase the safety and in a sling and filled with lactated Ringer’s solution. The improve the yield of pericardiocentesis. needle stabilizer was attached to the epicardial surface with two to four 4-O silk sutures. After a 5 min equilibration period, the blunt-tipped pacing needle electrode was ad- Methods vanced through the rubber diaphragm, and electrograms Pacing needle electrode and needle stabilizer. The pacing were recorded at 3 mm from the epicardial surface and after needle electrode for closed chest studies consisted of an 18 light contact with the surface. With the needle electrode in or 20 gauge spinal needle insulated along the length of the light contact with the epicardial surface, a spinal needle barrel with shrinkable Teflon tubing so that only 3 mm of the stylette was advanced through the barrel of the electrode and tip was exposed. The hub of the needle was soldered to a the epicardial surface was intentionally penetrated to a depth multistranded stainless steel insulated wire that could be of 2 mm. The stylette was then removed and the electrogram connected alternatively to a current source or to the ECG set recorded. This procedure was performed in six dogs at 26 to record a precordial lead (Fig. IA). For open chest studies, sites (14 sites over the right ventricle and 12 over the left the pacing needle electrode was modified by grinding off the ventricle). In addition, in five of the six dogs, after epicardial bevel of the needle so that the tip was square (Fig. 1B). penetration, the needle electrode was withdrawn to 3 mm Again, only 3 mm of the tip was exposed. To pace and record from the epicardial surface and another electrogram was electrograms from a fixed and reproducible distance from the recorded. This final recording, 3 mm from the epicardial heart, a needle-stabilizing device was constructed (Fig. 1C). surface after intentional epicardial penetration, was per- 1076 TWEDDELL ET AL. JACC Vol. 14, No. 4 PULSE GENERATOR-GUIDED PERICARDIOCENTESIS October 1989: 1074-83 formed over 17 sites in these five dogs (8 sites over the right then closed with a watertight stitch. The arterial pressure ventricle and 9 over the left ventricle). was measured through a catheter placed in the femoral Group II: open chest, open pericardium pacing study. To artery. Lactated Ringer’s solution was infused into the determine the optimal stimulus strength for pulse generator- pericardium until hemodynamic decompensation occurred guided pericardiocentesis, an open chest, open pericardium (mean arterial pressure 54 t- 10 mm Hg). The pulse genera- pacing study was performed. Five dogs were anesthetized, tor, stimulus strengths and pacing rates were the same as intubated and ventilated as before. Either a right fifth inter- those in Group II.