| 1. |
- Gottfridsson, Christer, 1958, et al.
(författare)
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Acute evaluation of transthoracic impedance vectors using ICD leads.
- 2009
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Ingår i: Pacing and clinical electrophysiology : PACE. - : Wiley. - 1540-8159 .- 0147-8389. ; 32:6, s. 762-71
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Minute ventilation (MV) has been proven to be very useful in rate responsive pacing. The aim of this study was to evaluate the feasibility of using implantable cardioverter-defibrillator (ICD) leads as part of the MV detection system. METHODS: At implant in 10 patients, the transthoracic impedance was measured from tripolar ICD, tetrapolar ICD, and atrial lead vectors during normal, deep, and shallow voluntary respiration. MV and respiration rate (RespR) were simultaneously measured through a facemask with a pneumotachometer (Korr), and the correlations with impedance-based measurements were calculated. Air sensitivity was the change in impedance per change in respiratory tidal volume, ohms (Omega)/liter (L), and the signal-to-noise ratio (SNR) was the ratio of the respiratory and cardiac contraction components. RESULTS: The air sensitivity and SNR in tripolar ICD vector were 2.70 +/- 2.73 ohm/L and 2.19 +/- 1.31, respectively, and were not different from tetrapolar. The difference in RespR between tripolar ICD and Korr was 0.2 +/- 1.91 breaths/minute. The regressed correlation coefficient between impedance MV and Korr MV was 0.86 +/- 0.07 in tripolar ICD. CONCLUSIONS: The air sensitivity and SNR in tripolar and tetrapolar ICD lead vectors did not differ significantly and were in the range of the values in pacemaker leads currently used as MV sensors. The good correlations between impedance-based and Korr-based RespR and MV measurements imply that ICD leads may be used in MV sensor systems.
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| 2. |
- Gottfridsson, Christer, 1958
(författare)
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Noninvasive characterization of patients with monomorphic ventricular tachycardia and ventricular fibrillation using the signal-averaged electrocardiogram. A study on late potentials and spectral turbulence in patients with ischemic heart disease and in healthy subjects.
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many people die suddenly from sustained ventricular tachyarrhythmias caused by ischemic heart disease, and the sudden death may be the first presentation of heart disease. If the patients at risk of ventricular tachyarrhythmia could be identified, some patients may be saved.The signal-averaged ECGs of 62 patients with spontaneous sustained monomorphic ventricular tachycardia (MVT), 64 survivors of cardiac arrest with ventricular fibrillation (VF), and 82 patients without ventricular arrhythmia who all had ischemic heart disease but no bundle branch block were compared. The patients with MVT frequently had a low ventricular ejection fraction and were significantly more late potential-positive and spectral turbulence-positive, which indicates that a more severe underlying substrate is necessary for development of MVT than for VF. The best variables of the signal-averaged ECG for identifying patients that had already suffered MVT vs VF were the width of the QRS complex measured as the filtered QRS duration and as the total QRS duration in the spectral analysis and the filtered QRS duration, respectively.The presence of a bundle branch block in patients with ischemic heart disease will per definition cause a wide QRS 3 120 ms and is known to further increase the risk of cardiac mortality. Patients with right bundle branch block (n=15) and with left bundle branch block (n=28) without spontaneous ventricular arrhythmias were late potential-positive in 27% and 50%, respectively, and spectral turbulence-positive in 80% and 79%, respectively. There were differences in the time domain analogous variables of the individual X, Y, Z orthogonal leads of the signal-averaged ECG between right and left bundle branch blocks. Patients with both spontaneous sustained MVT (n=13) or cardiac arrest with VF (n=6) and a bundle branch block were compared with control patients (n=38), matched 2:1 for each arrhythmia patient according to type of block, age, gender and previous myocardial infarction. There was no significant difference between patients with bundle branch block and VF and matched controls in any variable of the signal-averaged ECG, but the patients with MVT were more positive in variables of spectral analysis from individual X, Y, Z leads.In 121 subjects (55 men and 66 women; mean age 50 years) randomly selected without known heart disease and without bundle branch block, 7% were late potential-positive and 7% were spectral turbulence-positive. Almost all were completely normal at echocardiographic examination and during 24-hour ECG recording. The men had a significantly longer filtered QRS duration than women, which correlated with body surface area and intracardiac dimensions at echocardiography, but women had a longer QT interval in the 12 lead ECG. The numerical short-term reproducibility of the signal-averaged ECG variables was measured in the 121 healthy subjects. It was found to be good for time-domain and time-domain analogous variables but varied in spectral turbulence variables and was not different from short-term reproducibility in the 43 patients with bundle branch block or from long-term reproducibility. The reproducibility was affected by the noise level, but to a lesser extent by gender and age. If the spectral turbulence variable interslice-correlation standard deviation was replaced by the mean peaks per slice, the diagnostic reproducibility of spectral turbulence analysis improved substantially.
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| 3. |
- Gottfridsson, Christer, 1958, et al.
(författare)
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Sex difference and factors associated with outcome in patients with sustained ventricular arrhythmias.
- 2008
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Ingår i: Scandinavian cardiovascular journal : SCJ. - : Informa UK Limited. - 1401-7431 .- 1651-2006. ; 42:3, s. 182-91
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To describe gender differences and factors of importance for outcome in patients referred for sustained ventricular arrhythmias. RESULTS: Two hundred and fifty three patients took part in the survey, 126 (20 women) had sustained monomorphic ventricular tachycardia (VT) and 127 (31 women) had polymorphic VT/ventricular fibrillation. Ischemic heart disease was less common in women than in men (47 vs. 80%). At discharge, an ICD implant was similarly common in women (33%) and men (29%). One hundred and twenty five (65%) men and 37 (79%) women were alive at follow-up, p =0.08 (median follow-up 53 months). Independent predictors of long-term mortality were: 1) PVT/VF as the presenting arrhythmia, 2) a low ejection fraction, 3) increased QRS duration and 4) diabetes mellitus. CONCLUSION: The lower proportion of women compared to men being referred for evaluation of sustained ventricular arrhythmias may contribute to the lower number of ICD implants in women. The long-term survival in women and men did not differ significantly.
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| 4. |
- Gottfridsson, Christer, 1958, et al.
(författare)
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Spectral turbulence and late potentials in the signal-averaged electrocardiograms of patients with monomorphic ventricular tachycardia versus resuscitated ventricular fibrillation.
- 2000
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Ingår i: Scandinavian cardiovascular journal : SCJ. - 1401-7431. ; 34:3, s. 261-71
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Tidskriftsartikel (refereegranskat)abstract
- Signal-averaged electrocardiograms (SAECG) were analyzed for late potentials and spectral turbulence in 208 patients with ischemic heart disease with a history of sustained monomorphic ventricular tachycardia (MVT) (n = 62), resuscitation from ventricular fibrillation (VF) (n = 64) or no ventricular tachyarrhythmia (n = 82). Receiver operating characteristic curves were utilized to optimize cut-off values for prediction of MVT and VF. Patients with MVT had a lower ejection fraction (mean = 0.37) than patients with VF (0.44; p = 0.01) and controls (0.48; p < 0.0001). The mean FQRSD in MVT patients (126 ms) was longer than in VF and controls (113 ms; p = 0.005 and 102 ms; p < 0.0001, respectively). The RMS40 was lower in MVT (19 microV) than in VF and controls (29 microV; p = 0.0003 and 28 microV; p < 0.0001, respectively); 81% of the MVT patients were spectral turbulence-positive vs 47% of VF patients and 31% of control patients (p < 0.0001 for both differences). With optimized reference values, FQRSD, TQRSD and ISCSD contributed significantly to the identification of MVT patients and FQRSD to VF patients. The sensitivity of combined time-domain and spectral turbulence analysis was 90% for MVT and 58% for VF, with 63% specificity. MVT patients had a lower ejection fraction and were more often late potential and spectral turbulence positive than VF and control patients. These findings indicate that a large electroanatomic substrate is required in MVT. A long FQRSD was a risk marker for both MVT and VF. Spectral turbulence analysis added independent information, and the combination of time-domain and spectral turbulence analysis was superior to either method alone in identifying the MVT patients. Neither method of analysis, singly nor in combination, performed satisfactorily in identification of VF risk.
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| 5. |
- Gottfridsson, Christer, 1958, et al.
(författare)
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The short-term and long-term reproducibility of spectral turbulence and late potential variables of the signal-averaged ECG in a population sample of healthy subjects and the impact of gender, age, and noise.
- 2000
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Ingår i: Journal of electrocardiology. - 0022-0736. ; 33:2, s. 107-17
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Tidskriftsartikel (refereegranskat)abstract
- Previous methods for frequency domain analysis of the signal-averaged ECG (SAECG) have had low reproducibility. The reproducibility of time domain late potential analysis and spectral turbulence analysis was evaluated with 2 immediately consecutive SAECG recordings in 121 randomly selected subjects without heart disease (short-term) and also in 47 subjects after 1 month (long-term). A test was late potential positive if 2 or more of 3 variables were outside the reference limits and spectral turbulence positive if the score was 3 or 4. The short-term reproducibility was high for the filtered QRS duration (FQRSD), root mean square amplitude of the last 40 ms (RMS40) and high frequency low amplitude signals less than 40 microV (HFLAS40) of the time domain and total QRS duration (TQRSD), power spectral density of the last 40 ms and the late potential duration of time domain analogous analyses. The Spearman rank order correlation coefficients were 0.89, 0.88, and 0.84 and 0.97, 0.91 and 0.97, respectively. The reproducibility of the spectral score variables varied, and the correlation for the low slice correlation ratio was 0.71, spectral entropy 0.61, interslice correlation mean 0.58, and interslice correlation SD 0.28. A diagnostic inconsistency between 2 tests occurred in 0 (0%) subjects in late potential analysis if FQRSD was required for positivity, and in 7 (6%) otherwise, and in 9 (7%) of spectral turbulence analysis. If the spectral variable mean peaks per slice, with a correlation of 0.89, replaced interslice correlation SD in the spectral score, diagnostic inconsistency occurred in 0 (0%) subjects. The reproducibility seemed higher in women and in younger people but significantly only for interslice correlation subjects mean and HFLAS40. The long-term reproducibility did not differ significantly from short-term for any variable. In conclusion, the reproducibility was high in all time domain and time domain analogous variables. It varied among the spectral turbulence score variables and was very low for interslice correlation SD. The reproducibility of the spectral score improved substantially if this variable was replaced by mean peaks per slice.
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| 6. |
- Gottfridsson, Christer, 1958, et al.
(författare)
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The signal-averaged electrocardiogram before and after electrical cardioversion of persistent atrial fibrillation-implications of the sudden change in rhythm.
- 2011
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Ingår i: Journal of electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 44:2, s. 242-250
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Atrial fibrillation (AF), electrical cardioversion (direct current, or DC) shock energy, and a sudden change to sinus rhythm (SR) might all influence the interpretation of the signal-averaged electrocardiogram (SAECG) as risk markers of ventricular tachyarrhythmia. METHODS: The SAECG was recorded in 82 patients with persistent AF before and 2 hours after DC and analyzed for ventricular late potentials (LPs) and spectral turbulence. RESULTS: Sixty-nine patients (84%) obtained SR. Their mean (SD) heart rate decreased by 22 (20) beats/min, and the QTcF interval was significantly prolonged, 17 (38) milliseconds, as was the filtered QRS duration, 1.1 (4.7) milliseconds (40 Hz). The proportion of LP positivity (20%) did not change with the change in rhythm. Eight of 60 spectral turbulence-negative patients before DC became positive after DC (P = .01). The change in SAECG variables did not correlate significantly with the amount of energy delivered at DC. CONCLUSION: The LP analysis provided similar results in AF and SR, whereas the spectral turbulence analysis was more abnormal in SR. The electrical shock itself did not seem to explain this phenomenon.
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| 7. |
- Sandstedt, Bengt, 1951, et al.
(författare)
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Testing the implantable cardioverter-defibrillator after implantation--is it necessary?
- 2007
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Ingår i: Pacing Clin Electrophysiol. - 0147-8389. ; 30:8, s. 985-91
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Tidskriftsartikel (refereegranskat)abstract
- The results of intraoperative and postoperative predischarge implantable cardioverter-defibrillator (ICD) testing of 211 consecutive patients, starting at 15 J and requiring two successful terminations of induced VT/VF with a relative defibrillation safety margin (DSM) of >10 J, were reviewed. The aim was to define the type of intraoperative response that would make postoperative predischarge testing unnecessary. The intraoperative responses were divided into three types: A, a DSM > or =10 J and an absolute energy level of < or =20 J; B, a DSM of > or =10 J and an absolute energy level of >20 J; and C, a DSM <10 J and an absolute energy level of >20 J. At operation, the responses to defibrillation were A, 88.6%; B, 7.1%; and C, 4.3%. Accepting an A response only would leave 11.4% of the patients for postoperative testing. The positive and negative predictive values for diagnosing a postoperative C response were 0.78 and 0.97, respectively. Similarly, the predictive values for diagnosing a postoperative B or C response were 0.71 and 0.97, respectively. The postoperative testing responses were A, 89.1%; B, 4.3%; and C, 6.6%. In summary, an intraoperative A response was sufficient to make a postoperative defibrillation testing unnecessary, while it was found that intraoperative B and C responders should undergo postoperative testing. Applying these criteria, approximately 90% of the patients could be discharged without any postoperative induction test.
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