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Biomedical subjects

G W Dalzell

Publications and source records attributed to G W Dalzell.

At least 19 recordsLinked to original sources
PubMed1999

Randomised comparison of electrode positions for cardioversion of atrial fibrillation.

OBJECTIVE: To compare the relative efficacy of anteroanterior v anteroposterior electrode pad positions for external cardioversion of atrial fibrillation. DESIGN: Prospective randomised trial. SETTING: Tertiary referral cardiology centre in the United Kingdom. PATIENTS: 90 patients undergoing elective cardioversion for atrial fibrillation. INTERVENTIONS: Cardioversion was attempted with self adhesive electrode pads with an area of 106 cm2 placed either in the anteroanterior (AA) or anteroposterior (AP) positions. Initial shock was 100 J which, if unsuccessful, was followed by 200 J, 300 J, and 360 J if required. Peak current and transthoracic impedance were measured. MAIN OUTCOME MEASURES: Cardioversion success rate and energy requirements. RESULTS: Cardioversion was successful in 81% of the patients (73/90). There was no statistically significant difference in the cardioversion success rate (AA 84%, 38/45 patients; AP 78%, 35/45 patients; p = 0.42) or mean (SD) energy requirement for all patients (AA 223 (96.1) J; AP 232 (110) J) or for patients who were successfully cardioverted (AA 197.9 (82.4) J; AP 195.4 (97.2) J; p = 0.9) between the two pad positions. The mean transthoracic impedance (TTI) for the first shock (AA 77.5 (18.4) ohms; AP 73.7 (18.7) ohms; p = 0.34) was not significantly different between the two groups. TTI correlated significantly with body mass index, percentage body fat, and chest AP diameter. There was a progressive decrease in TTI with serial shocks. While aetiology and TTI were the two independent significant predictive factors for energy requirement, duration of atrial fibrillation was the only independent predictor of cardioversion success in a multivariate analysis. CONCLUSIONS: Electrode pad position is not a determinant of cardioversion success rate or energy requirement.

Aged↗
PubMed1997

Venous thrombosis causing arterial embolization to the same limb through a patent foramen ovale.

We describe a patient who presented with acute ischemia affecting the left lower limb. Because a transthoracic echocardiogram was abnormal, a transesophageal study was arranged. This demonstrated an atrial septal aneurysm and right-to-left shunting of contrast, raising the possibility of paradoxical embolism. The diagnosis was confirmed by contrast venography, which showed extensive thrombosis in the deep veins of the left thigh, and a ventilation-perfusion scan which was consistent with multiple pulmonary emboli. Among the lessons from this case was the finding that in patients with arterial embolism the likely origin of the embolus should be considered and, in the absence of common risk factors (atrial fibrillation, rheumatic heart disease, left ventricular dilatation, widespread atheroma), occult venous thrombosis and a right-to-left shunt should be sought. In this select group of patients, transesophageal echocardiography is significantly more sensitive than transthoracic study and should be the investigation of choice. Second, in the patient described in this report the clinical signs of deep venous thrombosis (DVT) were masked by the more prominent features of acute arterial ischemia. Without the incidental echocardiographic abnormality, it is likely that the important diagnoses of DVT, pulmonary embolism, and paradoxical embolism would not have been made.

Angiography↗
PubMed1997

A survey of exercise based cardiac rehabilitation services in Northern Ireland.

A survey was undertaken to establish the extent of provision of phase III exercise-based cardiac rehabilitation in Northern Ireland. Detailed information was obtained on patient referral mechanisms, patient assessment, the exercise component of cardiac rehabilitation and the use of outcome measures. The results suggest that cardiac rehabilitation in Northern Ireland has developed on an ad hoc basis, and although most centres accept myocardial infarction and coronary artery bypass graft patients for cardiac rehabilitation, higher risk patients are generally excluded from these programmes. Currently, little in the way of standard outcome measures are being used to evaluate the effectiveness of existing cardiac rehabilitation services. This paper makes several recommendations to facilitate the development of a more standardised service within Northern Ireland.

Coronary Artery Bypass↗
PubMed1993

Double-blind randomized trial of alteplase versus placebo in patients with chest pain at rest.

Patients who have chest pain occurring at rest are at a significant risk of myocardial infarction and or sudden death. Most trials enter patients with anginal rest pain after an initial screening period. Thus, the clinical efficacy of early thrombolytic treatment for patients with rest pain remains unproven. Eighty patients with chest pain at rest and with ECG changes of ST depression of at least 1 mm in any ECG lead, were randomized to alteplase 100 mg infused over 3 h, or placebo. Concomitantly, all patients received intravenous heparin and 300 mg of aspirin daily (unless contra-indicated). Seventy-four patients had coronary angiography (the majority within 72 h of admission) of which 73 were assessable. The patency of the ischaemia-related vessel was not significantly greater in the alteplase treated group (81% vs 78%, P = 0.82). The culprit lesion morphology tended to be more concentric in the alteplase treated group (84% vs 56%, P = 0.06) although alteplase treatment was not associated with a significant reduction in the severity of the culprit lesion stenosis. Intra-coronary thrombi were detected in 7% of patients (3% placebo, 11% alteplase, P = 0.35). The mean left ventricular ejection fraction or the alteplase-treated group was 49 +/- 3% and for the placebo-treated patients 56 +/- 3% (P = 0.05). There was no difference in the total in-hospital cardiac event rate i.e. cardiac death, myocardial infarction and coronary revascularization between patients receiving alteplase (10%, 63%, and 38%) and those receiving placebo (8%, 65%, and 30%) respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

The accuracy of decision-making of a semi-automatic defibrillator during cardiac arrest.

The accuracy of decision-making of a semi-automatic defibrillator was assessed at 57 cardiac arrests in 55 patients. The initial rhythm was ventricular fibrillation at 40 arrests and was correctly identified in 37 (sensitivity 92.5%). In the other 17 arrests initial rhythms were not ventricular fibrillation and 16 were correctly identified (specificity 94%). Continuous electrocardiographic recordings of the arrests were analysed in 8-12 s segments: of 432 segments showing ventricular fibrillation, 352 were correctly identified (sensitivity 81%); 3895 of 4139 segments showing rhythms other than ventricular fibrillation were correctly identified (specificity 94%). The percentage accuracy of detection of ventricular fibrillation varied from 0-100% (mean 91%) and for non-ventricular fibrillation from 51-100% (mean 92%). When 104 segments of ventricular fibrillation and 470 segments of non-ventricular fibrillation with cardiopulmonary resuscitation artefact were excluded from the analysis, a sensitivity of 91% and specificity of 96% were obtained. Thus the detection of cardiac arrest rhythms using a microprocessor based detection system for patients with cardiac arrest has a high sensitivity for ventricular fibrillation and specificity for non-ventricular fibrillation.

Cardiopulmonary Resuscitation↗
PubMed1991

Effectiveness of double bolus alteplase in the treatment of acute myocardial infarction.

Fifty-nine consecutive patients presenting within 6 hours of the onset of symptoms of an acute myocardial infarction were treated with 150 mg of soluble aspirin orally, and either 70 or 100 mg of alteplase divided into 2 intravenous bolus injections separated by 30 minutes. Dosage regimens were either 20 followed by 50 mg (group A), 50 followed by 20 mg (group B), or 50 followed by 50 mg (group C). Coronary angiography 60 minutes after the first bolus showed infarct-related coronary artery patency (Thrombolysis in Myocardial Infarction score 2 or 3) in 13 of 16 (81%) patients in group A, 12 of 17 (71%) in group B, and 10 of 11 (91%) in group C (overall patency rate at 60 minutes: 35 of 44 [80%] patients; 95% confidence interval 68 to 91%). At 90 minutes, patency rates were 15 of 20 (75%) patients in both groups A and B, and 18 of 19 (95%) in group C (overall patency rate 48 of 59 [81%] patients; 95% confidence interval 72 to 91%). Residual thrombus was identified with the 90-minute angiogram in 7 patients in group A, 5 in group B, and 3 in group C. Although there was no statistically significant difference in patency between the 3 dosage regimens at either 60 or 90 minutes there was a trend toward increased patency and more complete thrombolysis at 90 minutes in group C. No episodes of bradyarrhythmia, hypotension or cerebrovascular bleeding were observed after double bolus therapy. There were 7 episodes (12%) of reocclusion, and 3 deaths (5%) within 1-month follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

A cellular transtelephonic defibrillator for management of cardiac arrest outside the hospital.

A cellular transtelephonic defibrillator facilitates early defibrillation in remote areas and involves electrocardiographic diagnosis and defibrillation control by a physician remote from but in voice contact with the patient-unit operator. The patient unit contains a microprocessor, microphone, defibrillator, electrocardiogram/defibrillator electrode pads and cellular telephone. Activation of the patient-unit initiates automatic dialing and contact with the remotely sited base station within 35 to 50 seconds. The physician at the base station identifies the rhythm and controls defibrillator charging and discharge. The minimal interaction required between the system and the local operator makes it suitable for use by minimally trained first responders. The cellular transtelephonic defibrillator has been tested in 211 calls responded to by a physician-manned mobile coronary care unit over distances up to 15 miles in an urban area. Satisfactory electrocardiographic transmission and voice communication were established in 172 of 211 calls (81.5%). In 39 (18.5%), connection with the base station either could not be established or maintained mainly because of geographic location or battery failure. One hundred direct current shocks of 50 to 360 J were effectively administered to 22 patients with 48 episodes of ventricular fibrillation or ventricular tachycardia with successful correction of 46 of 48 episodes using 1 to 4 shocks per episode. Widespread distribution of such devices could improve survival in patients with cardiac arrest outside the hospital.

Ambulances↗
PubMed1991

Anistreplase in early acute myocardial infarction and the one-year follow-up.

Of consecutive patients seen with first myocardial infarction (88 of whom were treated out-of-hospital by mobile coronary care staff), 139 received 30 units of intravenous anistreplase at a mean of 101 minutes (range 35-180) from onset of symptoms. Thrombolysis in myocardial infarction patency grade 2 or 3 was found in 76/91 (83.5%) patients. At 3-4 months after hospital discharge, the mean global left ventricular ejection fraction and mean infarct-related regional third ejection fraction declined with increasing delay to anistreplase. For the first, second and third hour administrations, global ejection fraction was 54%, 50% and 45% (P = 0.002) and for regional third ejection fractions 49%, 43% and 41% (P = 0.02) respectively. Of the patients, 130 were reviewed at approximately 1 year: reinfarction had occurred in 9, 6 had undergone coronary angioplasty and 1 had coronary arterial bypass grafting performed since discharge. Mean global left ventricular ejection fraction was 52% and mean infarct-related regional third ejection fraction was 51%. Thus, intravenous anistreplase induces high rates of arterial patency. Global and regional third ejection fractions decline with increasing delay in the time of administration of anistreplase. Mortality and morbidity is low in the first year.

Adult↗
PubMed1991

Determinants of successful transthoracic defibrillation and outcome in ventricular fibrillation.

OBJECTIVE: To examine factors determining defibrillation success and outcome in patients with ventricular fibrillation. DESIGN: Observational prospective study of age, sex, transthoracic impedance, site of cardiac arrest, ventricular fibrillation duration and amplitude, primary or secondary ventricular fibrillation, aetiology, number of shocks to correct ventricular fibrillation, and drug treatment. SETTING: A teaching hospital and a mobile coronary care unit with a physician. PATIENTS: 70 consecutive patients (50 male, 20 female) mean age 66.5 years. INTERVENTIONS: Before the first countershock was administered transthoracic impedance using a 30 kHz low amplitude AC current passed through 8 cm/12 cm self-adhesive defibrillator electrode pads applied in the anteroapical position was measured. The first two shocks were 200 J delivered energy (low energy) and further shocks of 360 J (high energy) were given if required. MAIN OUTCOME MEASURES: Countershock success and outcome from ventricular fibrillation. RESULTS AND CONCLUSIONS: First shock success was significantly greater in inhospital arrests (37/53) than in out-of-hospital arrests (5/17) and in those receiving antiarrhythmic treatment (13/15, 86.7%) v (27/51, 52.9%). Transthoracic impedance was similar in those who were successfully defibrillated with one or two 200 J shocks (98.7 (26) omega) and those who required one or more 360 J shocks (91.4 (23) omega). Success rates with two 200 J shocks were similar in those patients with "high" transthoracic impedance (that is, greater than 115 omega) and those with transthoracic impedance (less than or equal to 115 omega) (8/12 (67%) v 44/58 (76%]. Fine ventricular fibrillation was significantly more common in the patients with a transthoracic impedance of greater than 95 omega (41% (13/32] than in those with a transthoracic impedance less than or equal to 95 omega (13% (5/38]. Death during arrest was significantly more common in patients who needed high energy shocks (14/18 (78%] than in those who needed low energy shocks (16/52 (31%]. Multiple regression analysis identified ventricular fibrillation with an amplitude of greater than or equal to 0.5 mV, age less than or equal to 70 years, and arrests that needed less than or equal to two shocks for defibrillation, in rank order as independent predictors of survival to discharge.

Aged↗
PubMed1991

Factors determining success and energy requirements for cardioversion of atrial fibrillation: revised version.

Factors thought to affect the success of and energy requirements for cardioversion of atrial fibrillation were studied in 80 (49 male, 31 female) patients aged 21-88 (mean 61.5 years). Transthoracic impedance was measured in advance of the countershock using a 30 kHz low amplitude AC current passed through self-adhesive ECG/defibrillator pads (diameters 8 and 12 cm) applied to the chest in the antero-posterior (AP) position in 57 patients and the anteroapical (AA) position in 23 patients. Mean transthoracic impedance for all patients was 69.3 +/- 16 (SD) ohms (range 39-131 ohms), but transthoracic impedance was significantly greater in the AA than the AP position (75.4 +/- 13 vs. 66.7 +/- 16 ohms, p = 0.02). Initial energy was 50 J (delivered) and was gradually increased to a maximum of 360 J if required. Cardioversion was successful in 73 of 80 (91.2 per cent), and low energy shocks (< or = 200 J) were successful in 45 of 80 (56.2 per cent) patients. Using single factor analysis, sex, left atrial enlargement, electrode pad positions, aetiology of atrial fibrillation, presence of left ventricular failure, and prior treatment with verapamil or beta-adrenergic blockers were not significant determinants of cardioversion success or success of low energy shocks but prior treatment with digoxin was, both for cardioversion success and success at low energies. In patients with transthoracic impedance < or = 70 ohms, low energy shocks were more often successful (33 of 50, 66 per cent) than in patients with transthoracic impedance > 70 ohms (12 of 30, 40 per cent), p = 0.04. Using univariate analysis, cardioversion success with low energy shocks was not only significantly associated with prior treatment with digoxin but also with the duration of atrial fibrillation (24 hours to less than one month and one month to three years) and for shocks of < or = 100 J, with prior treatment with amiodarone. Multifactorial linear regression analysis selected, in rank order, only duration of atrial fibrillation of 24 hours to less than one month and one month to three years as significant predictors of both cardioversion success irrespective of shock strength, and success of low energy shocks.

Adult↗
PubMed1991

Thrombolytic therapy within one hour of the onset of acute myocardial infarction.

Between 1986 and 1988, 239 consecutive patients with acute myocardial infarction received thrombolytic therapy up to 285 minutes after onset of symptoms; in 39 (17 with anterior infarction, 21 inferior, one lateral infarction) recombinant tissue plasminogen activator or anistreplase was administered a mean of 51 minutes (range 20-60 minutes) after the onset of symptoms. The patency rates (26 of 30; 87 per cent), rapid ST segment resolution (36 of 38; 95 per cent) and QRS score of less than or equal to 3 (28 of 38; 74 per cent) were statistically significantly higher for those seen and treated in the first hour in comparison with those seen and treated later. For those treated within the first hour mean peak creatine kinase was 1264 U/l for those with TIMI grade 2 or 3 (partial or complete perfusion) compared with 3005 U/l for those with TIMI grade 0 or 1 (no perfusion or penetration without perfusion) (p = 0.02): mean peak creatine kinase-MB for those with TIMI grade 2 or 3 perfusion was 115 U/l compared with 312 U/l for those with TIMI grade 0 or 1 (p = 0.01). Four of the 39 patients developed ventricular fibrillation following thrombolytic therapy, three within 24 hours of infarction and one following reinfarction on day 15. There were no significant bleeding complications. One patient died. Thrombolytic therapy within 1 hour of the onset of symptoms led to a very high angiographic patency rate, rapid ST segment resolution with preservation of left ventricular function. This therapy is without significant complications.

Anistreplase↗
PubMed1991

The initial electrocardiogram in patients seen by a mobile coronary care unit.

The advent of thrombolytic therapy for patients with suspected acute myocardial infarction has highlighted the importance of the initial electrocardiogram (ECG) in decision making. Thus we analysed the initial ECGs of 94 consecutive cases with suspected myocardial infarction who were seen within six hours after the onset of chest pain by a mobile coronary care unit. The study included 91 patients (three patients admitted twice) (61 male), aged 27-83 years (mean 60.5). Median time from onset of chest pain to arrival of the mobile coronary care unit was 75 minutes (range 15-345), and mean mobile coronary care unit response time was 12.3 +/- 7 (SD) minutes (range 5-45). The majority of cases (65 of 94, 69.1 per cent) were seen within two hours of the onset of symptoms. A final diagnosis of myocardial infarction was made in 48 of 94 (51.1 per cent) cases; 38 had unstable angina and eight other diagnoses. Of the 48 with myocardial infarction the initial ECG showed ST segment elevation in 37, ST depression and or T wave inversion in six, Q waves only in three and left bundle branch block in two. No patient with an initially normal ECG had a myocardial infarction. Thrombolytic therapy was given out of hospital to 33 of 38 patients with ST segment elevation. In seven patients with ST elevation (median delay time to intensive care 60 minutes), rapid resolution of ST segment elevation occurred following thrombolytic therapy and there was no significant elevation of cardiac enzymes, suggesting that the infarct had been aborted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Factors determining success and energy requirements for cardioversion of atrial fibrillation.

Factors thought to affect the success of and energy requirements for cardioversion of atrial fibrillation were studied in 80 (49 male, 31 female) patients aged 21-88 (mean 61.5 years). Transthoracic impedance was measured in advance of the countershock using a 30 kHz low amplitude AC current passed through self-adhesive ECG/defibrillator pads (diameters 8-12 cm) applied to the chest in the antero-posterior (AP) position in 57 patients and the anteroapical (AA) position in 23 patients. Mean transthoracic impedance for all patients was 69.3 +/- 16 (SD) ohms (range 39-131 ohms), but transthoracic impedance was significantly greater in the AA than the AP position (75.4 +/- 13 vs. 66.7 +/- 16 ohms, p = 0.02). Initial energy was 50 J (delivered) and was gradually increased to a maximum of 360 J if required. Cardioversion was successful in 73 of 80 (91.2 per cent), and low energy shocks (less than or equal to 200 J) were successful in 45 of 80 (56.2 per cent) patients. Using single factor analysis, sex, left atrial enlargement, electrode pad positions, aetiology of atrial fibrillation, presence of left ventricular failure, and prior treatment with verapamil or beta-adrenergic blockers were not significant determinants of cardioversion success or success of low energy shocks but prior treatment with digoxin was, both for cardioversion success and success at low energies. In patients with transthoracic impedance less than or equal to 70 ohms, low energy shocks were more often successful (33 or 50, 66 per cent) than in patients with transthoracic impedance greater than 70 ohms (12 of 30, 40 per cent), p = 0.04. Using univariate analysis, cardioversion success with low energy shocks was not only significantly associated with prior treatment with digoxin but also with the duration of atrial fibrillation (24 hours to one month and one month to three years) and for shocks of less than or equal to 100 J, with prior treatment with amiodarone. Multifactorial linear regression analysis selected, in rank order, only duration of atrial fibrillation of 24 hours to less than one month and one month to three years as significant predictors of both cardioversion success irrespective of shock strength, and success of low energy shocks.

Adult↗
PubMed1989

Electrode pad size, transthoracic impedance and success of external ventricular defibrillation.

Electrode pad size is an important determinant of transthoracic current flow during external countershock. Self-adhesive, dual function electrocardiogram/defibrillator pads were used to assess the effect of electrode pad size on defibrillation success with low energy (200 J) shocks. The study analyzed 123 cardiac arrests due to primary ventricular fibrillation (VF) in 105 patients (74 men, 31 women) ages 40 to 84 years (mean 64). Transthoracic impedance was measured before defibrillation using a low amplitude 30-kHz current passed through the chest by way of the electrocardiogram/defibrillator pads applied anteroanteriorly. Pad diameters were small (8/8 cm) in 26 cardiac arrests, intermediate (8/12 cm) in 63 arrests and large (12/12 cm) in 34 cardiac arrests. Transthoracic impedance decreased with increasing pad size (112 +/- 17 vs 92 +/- 22 vs 72 +/- 14 omega, respectively, p = 0.0001). Only the first episode of primary VF during a cardiac arrest was analyzed. A single shock of 200 J (delivered energy) was successful in 8 of 26 (31%) arrests using small pads, in 40 of 63 (63%) with intermediate pads and in 28 of 34 (82%) with large pads (p = 0.0003). A second 200-J shock increased the cumulative defibrillation rates to 12 of 26 (46%), 50 of 63 (79%) and 33 of 34 (97%), respectively (p less than 0.0001). In primary VF, larger self-adhesive electrocardiogram/defibrillator pads are associated with a lower transthoracic impedance and improved defibrillation success rates with low energy shocks.

Adhesives↗
PubMed1989

A double blind placebo controlled study of early and late administration of recombinant tissue plasminogen activator in acute myocardial infarction.

Within four hours of the onset of acute myocardial infarction 57 consecutive patients were randomised blindly to infusion of 150 mg recombinant tissue plasminogen activator (rt-PA) (group 1) over five hours or placebo (group 2) when they were first seen outside hospital or in the accident and emergency department. When they were admitted to the coronary care unit patients in group 1 also had placebo infused and those in group 2 were treated with rt-PA as well as placebo. Treatment with rt-PA started at a mean of 119 minutes (range 38-235) after the onset of pain in group 1 and 187 minutes (range 80-285) after the onset of pain in group. In 19 (79%) of 24 in group 1 and 16 of 25 (64%) in group 2 cardiac catheterisation 10-14 days after infarction showed thrombolysis in myocardial infarction grades 2 or 3. There was mean percentage shortening of the infarct related segments (Leighton method) of 16% in group 1 and 10.3% in group 2. For patients with anterior infarction mean percentage shortening was 20.5% in group 1 and 12.2% in group 2. Although there was no significant difference in global ejection fraction as assessed by contrast ventriculography or radionuclide ventriculography the infarct related regional third ejection fraction (a measure of the function of the territory of the affected coronary artery) was significantly improved by early treatment (41% group 1 and 28% group 2). Assessment of infarct size by the QRS scoring method of Palmeri showed QRS score less than or equal to 15/25 patients in group 1 and 8/27 in group 2. Nine patients developed 11 episodes of ventricular fibrillation; all patients in whom ventricular fibrillation developed during treatment with rt-PA were successfully resuscitated. There was no clinically significant bleeding. In seven (12%) patients clinical and electrocardiographic criteria suggested reocclusion. Five patients died from cardiac causes. Prehospital administration of rt-PA was feasible and significantly reduced the delay before thrombolysis was started. Earlier treatment improved myocardial function in the the infarct area and reduced the infarct size.

Adult↗
PubMed1989

Initial experience with a microprocessor controlled current based defibrillator.

Intramyocardial current flow is a critical factor in successful ventricular defibrillation. The main determinants of intramyocardial current flow during transthoracic countershock are the selected energy and the transthoracic impedance of the patient. To optimise the success of the first shock and to titrate energy dosage according to each patient's transthoracic impedance, a microprocessor controlled current based defibrillator was developed. It was compared with a conventional energy based protocol of 200 J (delivered energy), 200 J, then 360 J if required in 42 consecutive episodes of ventricular fibrillation in 33 men and seven women. The mean (SD) predicted transthoracic impedance was 69.9 (14.0) omega. First shock success with the standard protocol was 80.9%, and first or second shock success was 95.2%. The microprocessor controlled current based defibrillator automatically measured transthoracic impedance and calculated the energy required to develop a selected current in each patient. A current protocol of 30 A, 30 A, then 40 A, if required, was used in 29 men and 12 women with 41 episodes of ventricular fibrillation. Transthoracic impedance (mean 65.1 (15.9) omega) was similar to that in the energy protocol group and success rates for first shock (82.9%) and first or second shocks (97.5%) were also similar. The mean delivered energy per shock with the current based defibrillator for first or second shock success was significantly less (144.8 J) with the energy protocol (200 J). The mean peak current of successful shocks was also significantly reduced (29.0 v 31.9 A). A current based defibrillator titrates energy according to transthoracic impedance; it has a success rate comparable to conventional defibrillators but it delivers significantly less energy and current per shock.

Cardiography, Impedance↗