title: Cardiovascular responses to repetitive defibrillation during implantable cardioverter-defibrillator testing.
abstract: OBJECTIVE
  To study the effects of electrical applications and subsequent postshock hypotension on myocardial performance and vascular tone during implantable cardioverter-defibrillator (ICD) placement.
  
  
  METHODS
  Prospective, blinded, observational investigation.
  
  
  METHODS
  Single, university-affiliated institution.
  
  
  METHODS
  Twenty patients undergoing elective ICD placement and testing under general anesthesia.
  
  
  METHODS
  None.
  
  
  RESULTS
  Serial measurements were made of hemodynamic variables, left ventricular end-systolic (ESA) and end-diastolic (EDA) areas, fractional-area-of-contraction (FAC), time of hypoperfusion (when mean arterial pressure < or =50 mmHg postshock), and applied conversion energy. Multiple linear regression was performed to determine correlations among collected variables, and repeated measures analysis of variance was used to compare mean values. Minimal changes were detected in mean values of arterial, pulmonary, and central venous pressures; cardiac output; heart rate; and mixed venous saturation during repeated testing. Percentage changes in cardiac index (CI) rose and systemic vascular resistance index (SVRI) fell, however, as the number of shocks increased, reaching significance at the seventh and eighth shocks (v baseline; both p = 0.015). The percentage change in CI was linearly related to hypoperfusion time and accumulated energy (%deltaCI = 1.553 + [0.068 x sigma hypoperfusion time [sec]], r = 0.92, p < 0.001; %deltaCI = 0.326 + [0.125 x sigma Energy [J]], r = 0.94, p < 0.001). The percentage change in SVRI was inversely related to hypoperfusion time and accumulated energy (%deltaSVRI = 2.195 - [0.122 x sigma energy [J]], r = 0.79, p = 0.004; %deltaSVRI = 0.542 - [0.0634 - sigma hypoperfusion time [sec]], r = 0.73, p = 0.01). Echocardiographic EDA, ESA, and FAC were not significantly changed but showed substantial variability.
  
  
  CONCLUSIONS
  Hemodynamic stability was generally well maintained during ICD placement and testing. Increases in CI were associated with concurrent reductions in systemic afterload, rather than enhanced FAC. Increasing postshock hypotension and applied energy were associated with decreases in CI and systemic afterload. Insignificant, but highly variable, changes were noted echocardiographically.
authors.affiliation: Departments of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD 21201-1595, USA. tgilbert@anesthesia.ummc.umaryland.edu
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Gilbert
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Shorofsky
authors.forename: Jawad U
authors.initials: JU
authors.lastname: Hasnain
authors.forename: Mary K
authors.initials: MK
authors.lastname: Ferguson
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Foster
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General; D017147:Defibrillators, Implantable; D017548:Echocardiography, Transesophageal; D004554:Electric Countershock / Q000009:adverse effects; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007022:Hypotension / Q000209:etiology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D013614:Tachycardia, Paroxysmal / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy