Outcome after rewarming from accidental hypothermia by use of extracorporeal circulation

Background: Accidental hypothermia with arrested circulation remains a condition associated with high mortality. In our institution, extracorporeal circulation (ECC) rewarming has been the cornerstone in treating such patients since 1987. We here explore characteristics and outcomes of this treatment, to identify significant merits and challenges from 3 decades of experience in ECC rewarming. Methods: Sixty-nine patients rewarmed by ECC during the period from December 1987 to December 2015 were analyzed. One patient was excluded from the analyses because of combined traumatic cerebral injury. The analysis was focused on patient characteristics, treatment procedures, and outcomes were focused. Survivors were evaluated according to the cerebral performance categories scale. Simple statistics with nonparametric tests and χ2 tests were used. Median value and range are reported. Results: Median age was 30 years (minimum 1.5, maximum 76), and the cause of accidental hypothermia was cold exposure (27.9%), avalanche (5.9%), and immersion/submersion accidents (66.2%). Eighteen patients survived (26.5%). The survival rate did not improve during the years. Survivors had lower serum potassium (p = 0.002), higher pH (p = 0.03), lower core temperature (p = 0.02), and shorter cardiopulmonary resuscitation time (p = 0.001), but ranges were wide. Although suspected primary hypoxia and hypothermia were associated with lower survival, we observed a 10.5% survival of these victims. Sixteen survivors had good outcome (cerebral performance category 1 or 2), whereas 2 patients with suspected primary hypoxia survived with severe cerebral disability (cerebral performance category 3). Conclusions: Despite extended experience with ECC rewarming, improved handling strategies, and intensive care, no overall improvement in survival was observed. Good outcome was observed even among patients with a dismal prognosis.publishedVersio

Effect of Temporal and Spatial Smoothing on Speckle–Tracking‑Derived Strain in Neonates

Clinical application of strain in neonates requires an understanding of which image acquisition and processing parameters affect strain values. Previous studies have examined frame rate, transmitting frequency, and vendor heterogeneity. However, there is a lack of human studies on how user-regulated spatial and temporal smoothing affect strain values in 36 neonates. This study examined nine different combinations of spatial and temporal smoothing on peak systolic left ventricular longitudinal strain in 36 healthy neonates. Strain values were acquired from four-chamber echocardiographic images in the software-defined epicardial, midwall, and endocardial layers in the six standard segments and average four-chamber stain. Strain values were compared using repeated measure ANOVAs. Overall, spatial smoothing had a larger impact than temporal smoothing, and segmental strain values were more sensitive to smoothing settings than average four-chamber strain. Apicoseptal strain decreased by approximately 4% with increasing spatial smoothing, corresponding to a 13–19% proportional change (depending on wall layer). Therefore, we recommend clinicians be mindful of smoothing settings when assessing segmental strain values.publishedVersio

Left ventricular venting during extracorporeal membrane oxygenation; the effects on cardiac performance in a porcine model of critical post-cardiotomy failure

Introduction Left ventricular distension is a major concern with postcardiotomy veno-arterial extracorporeal membrane oxygenation (VA-ECMO) supporting a critical heart failure after cardiac surgery. This porcine study evaluates the effects of left ventricular venting on cardiac function during ECMO-supported circulation and after weaning from ECMO. Methods Twenty anaesthetised open-chest pigs were put on cardiopulmonary bypass with aortic cross-clamping and suboptimal cardioplegic arrest for 40 min. After declamping and defibrillation, the animals were supported by VA-ECMO for 180 min either with or without additional left ventricular venting. Continuous haemodynamic evaluations were performed at baseline and at cardiac arrest, during VA-ECMO and for 120 min after weaning from circulatory support. Left ventricular perfusion and function were evaluated with microspheres, pressure-volume loops and epicardial echocardiography at baseline and after 1 and 2 h with unsupported circulation. Results In vented animals both mean aortic and left ventricular peak systolic pressure increased at the end of the ECMO-supported period compared to those not vented and remained increased also after weaning. Both at 60 min and 120 min after weaning from circulatory support, left ventricular stroke work and pressure-volume area were increased in vented compared to not vented animals. At 120 min left ventricular stroke volume was increased in vented compared to not vented animals, myocardial perfusion did not differ. The left ventricular mechanical efficiency, defined as the ratio between pressure volume area and myocardial perfusion, was increased (53.2 ± 5 vs 36.2 ± 2.1 J/mL/g, p = 0.011) in vented- compared to not vented hearts. Conclusion This experimental study demonstrate that left ventricular venting during post-cardiotomy veno-arterial ECMO for 3 h attenuates deterioration of left ventricular function and haemodynamics early after weaning from circulatory support.publishedVersio

Myocardial energy metabolism and ultrastructure with polarizing and depolarizing cardioplegia in a porcine model

OBJECTIVES: This study investigated whether the novel St. Thomas’ Hospital polarizing cardioplegic solution (STH-POL) with esmolol/adenosine/magnesium offers improved myocardial protection by reducing demands for high-energy phosphates during cardiac arrest compared to the depolarizing St. Thomas’ Hospital cardioplegic solution No 2 (STH-2). METHODS: Twenty anaesthetised pigs on tepid cardiopulmonary bypass were randomized to cardiac arrest for 60 min with antegrade freshly mixed, repeated, cold, oxygenated STH-POL or STH-2 blood cardioplegia every 20 min. Haemodynamic variables were continuously recorded. Left ventricular biopsies, snap-frozen in liquid nitrogen or fixed in glutaraldehyde, were obtained at Baseline, 58 min after cross-clamp and 20 and 180 min after weaning from bypass. Adenine nucleotides were evaluated by high-performance liquid chromatography, myocardial ultrastructure with morphometry. RESULTS: With STH-POL myocardial creatine phosphate was increased compared to STH-2 at 58 min of cross-clamp [59.9 ± 6.4 (SEM) vs 44.5 ± 7.4 nmol/mg protein; P < 0.025], and at 20 min after reperfusion (61.0 ± 6.7 vs 49.0 ± 5.5 nmol/mg protein; P < 0.05), ATP levels were increased at 20 min of reperfusion with STH-POL (35.4 ± 1.1 vs 32.4 ± 1.2 nmol/mg protein; P < 0.05). Mitochondrial surface-to-volume ratio was decreased with polarizing compared to depolarizing cardioplegia 20 min after reperfusion (6.74 ± 0.14 vs 7.46 ± 0.13 µm2/µm3; P = 0.047). None of these differences were present at 180 min of reperfusion. From 150 min of reperfusion and onwards, cardiac index was increased with STH-POL; 4.8 ± 0.2 compared to 4.0 ± 0.2 l/min/m2 (P = 0.011) for STH-2 at 180 min. CONCLUSIONS: Polarizing STH-POL cardioplegia improved energy status compared to standard STH-2 depolarizing blood cardioplegia during cardioplegic arrest and early after reperfusion.publishedVersio

Left ventricular dysfunction after two hours of polarizing or depolarizing cardioplegic arrest in a porcine model

Introduction: This experimental study compares myocardial function after prolonged arrest by St. Thomas’ Hospital polarizing cardioplegic solution (esmolol, adenosine, Mg2+) with depolarizing (hyperkalaemic) St. Thomas’ Hospital No 2, both administered as cold oxygenated blood cardioplegia. Methods: Twenty anaesthetized pigs on tepid (34°C) cardiopulmonary bypass (CPB) were randomised to cardioplegic arrest for 120 min with antegrade, repeated, cold, oxygenated, polarizing (STH-POL) or depolarizing (STH-2) blood cardioplegia every 20 min. Cardiac function was evaluated at Baseline and 60, 150 and 240 min after weaning from CPB, using a pressure-conductance catheter and epicardial echocardiography. Regional tissue blood flow, cleaved caspase-3 activity and levels of malondialdehyde were evaluated in myocardial tissue samples. Results: Preload recruitable stroke work (PRSW) was increased after polarizing compared to depolarizing cardioplegia 150 min after declamping (73.0±3.2 vs. 64.3±2.4 mmHg, p=0.047). Myocardial tissue blood flow rate was high in both groups compared to the Baseline levels and decreased significantly in the STH-POL group only, from 60 min to 150 min after declamping (p<0.005). Blood flow was significantly reduced in the STH-POL compared to the STH-2 group 240 min after declamping (p<0.05). Left ventricular mechanical efficiency, the ratio between total pressure-volume area and blood flow rate, gradually decreased after STH-2 cardioplegia and was significantly reduced compared to STH-POL cardioplegia after 150 and 240 min (p<0.05 for both). Conclusion: Myocardial protection for two hours of polarizing cardioplegic arrest with STH-POL in oxygenated blood is non-inferior compared to STH-2 blood cardioplegia. STH-POL cardioplegia alleviates the mismatch between myocardial function and perfusion after weaning from CPB.publishedVersio

Mitral annular dynamics are influenced by left ventricular load and contractility in an acute animal model

The purpose of this study was to investigate the effects of loading conditions and left ventricular (LV) contractility on mitral annular dynamics. In 10 anesthetized pigs, eight piezoelectric transducers were implanted equidistantly around the mitral annulus. High-fidelity catheters measured left ventricular pressures and the slope of the end-systolic pressure-volume relationship (Ees) determined LV contractility. Adjustments of pre- and afterload were done by constriction of the inferior caval vein and occlusion of the descending aorta. Mitral annulus area indexed to body surface area (MAAi ), annular circularity index (ACI), and nonplanarity angle (NPA) were calculated by computational analysis. MAAi was more dynamic in response to loading interventions than ACI and NPA. However, MAAi maximal cyclical reduction (−Δr) and average deformational velocity (−v) did not change accordingly (p=0.31 and p=0.22). Reduced Ees was associated to attenuation in MAAi -Δr and MAAi -v (r 2=0.744; p=0.001 and r 2=0.467; p=0.029). In conclusion, increased cardiac load and reduced LV contractility may cause deterioration of mitral annular dynamics, likely impairing coaptation and increasing susceptibility to valvular incompetence.publishedVersio

Carvedilol Retards Sudden Loss of Contraction during Early Regional Myocardial Ischemia in Feline Hearts 1

ABSTRACT The purpose of our study was to investigate whether loss of myocardial contraction immediately after coronary occlusion was nonuniform, and if pretreatment with carvedilol, a vasodilating nonselective ␤-adrenoceptor antagonist, could retard loss of contraction after coronary artery occlusion. Feline hearts were subjected to acute regional ischemia by total occlusion of the left anterior descending coronary artery. The animals were either treated with vehicle (control group) or with carvedilol 1 mg/kg i.v. before left anterior descending coronary artery occlusion (n ϭ 9 in each group). Regional contraction in the left anterior descending coronary artery perfused region of the heart was studied by cross-oriented sonomicrometry. In control animals, circumferential (subepicardial) contraction ceased after 10 sec, whereas longitudinal (subendocardial) contraction ceased immediately after left anterior descending coronary artery occlusion. Loss of contraction in animals treated with carvedilol was significantly slower compared to controls. Circumferential contraction ceased between 30 sec and 1 min, whereas longitudinal contraction ceased after 20 sec. In conclusion, loss of contraction during the first seconds after coronary occlusion was nonuniform, with most rapid dysfunction in the subendocardium. Pretreatment with carvedilol retarded loss of contraction in both axes. It has been known for many years that myocardial contraction ceases in the ischemic myocardium within just a few seconds after a coronary artery occlusion has occurred The subendocardium is more susceptible to ischemic injury than the subepicardium. Myocardial infarction starts in the subendocardium and spreads like a wavefront toward the subepicardium The protective effects of beta adrenoceptor antagonists on acute myocardial infarction are well established, particularly for lipophilic beta adrenoceptor antagonists without intrinsic sympathomimetic effects ABBREVIATIONS: LAD, left anterior descending coronary artery; EDL, end diastolic length; ESL, end systolic length; LVSP, left ventricular systolic pressure; LVEDP, left ventricular end diastolic pressure; RPP, rate pressure product

Outcome after rewarming from accidental hypothermia by use of extracorporeal circulation

Background: Accidental hypothermia with arrested circulation remains a condition associated with high mortality. In our institution, extracorporeal circulation (ECC) rewarming has been the cornerstone in treating such patients since 1987. We here explore characteristics and outcomes of this treatment, to identify significant merits and challenges from 3 decades of experience in ECC rewarming. Methods: Sixty-nine patients rewarmed by ECC during the period from December 1987 to December 2015 were analyzed. One patient was excluded from the analyses because of combined traumatic cerebral injury. The analysis was focused on patient characteristics, treatment procedures, and outcomes were focused. Survivors were evaluated according to the cerebral performance categories scale. Simple statistics with nonparametric tests and χ2 tests were used. Median value and range are reported. Results: Median age was 30 years (minimum 1.5, maximum 76), and the cause of accidental hypothermia was cold exposure (27.9%), avalanche (5.9%), and immersion/submersion accidents (66.2%). Eighteen patients survived (26.5%). The survival rate did not improve during the years. Survivors had lower serum potassium (p = 0.002), higher pH (p = 0.03), lower core temperature (p = 0.02), and shorter cardiopulmonary resuscitation time (p = 0.001), but ranges were wide. Although suspected primary hypoxia and hypothermia were associated with lower survival, we observed a 10.5% survival of these victims. Sixteen survivors had good outcome (cerebral performance category 1 or 2), whereas 2 patients with suspected primary hypoxia survived with severe cerebral disability (cerebral performance category 3). Conclusions: Despite extended experience with ECC rewarming, improved handling strategies, and intensive care, no overall improvement in survival was observed. Good outcome was observed even among patients with a dismal prognosis

Is strain by Speckle Tracking Echocardiography dependent on user controlled spatial and temporal smoothing? An experimental porcine study

Background Speckle Tracking Echocardiography (STE) strain analysis relies on both spatial and temporal smoothing. The user is often allowed to adjust these smoothing parameters during analysis. This experimental study investigates how different degrees of user controllable spatial and temporal smoothing affect global and regional STE strain values in recordings obtained from normal and ischemic myocardium. Methods In seven anesthetized pigs, left ventricular short- and long-axis B-mode cineloops were recorded before and after left anterior descending coronary artery occlusion. Peak- and postsystolic global STE strain in the radial, circumferential and longitudinal direction as well as corresponding regional strain in the anterior and posterior walls were measured. During post-processing, strain values were obtained with three different degrees of both spatial and temporal smoothing (minimum, factory default and maximum), resulting in nine different combinations. Results All parameters for global and regional longitudinal strain were unaffected by adjustments of spatial and temporal smoothing in both normal and ischemic myocardium. Radial and circumferential strain depended on smoothing to a variable extent, radial strain being most affected. However, in both directions the different combinations of smoothing did only result in relatively small changes in the strain values. Overall, the maximal strain difference was found in normal myocardium for peak systolic radial strain of the posterior wall where strain was 22.0 ± 2.2% with minimal spatial and maximal temporal smoothing and 30.9 ± 2.6% with maximal spatial and minimal temporal smoothing (P < 0.05). Conclusions Longitudinal strain was unaffected by different degrees of user controlled smoothing. Radial and circumferential strain depended on the degree of smoothing. However, in most cases these changes were small and would not lead to altered conclusions in a clinical setting. Furthermore, smoothing did not affect strain variance. For all strain parameters, variance remained within the corresponding interobserver variance

Long-term follow-up after surgery for atrial fibrillation with concomitant open heart surgery

BAKGRUNN Pasienter med atrieflimmer/flutter som skal gjennomgå en åpen hjerteoperasjon, kan behandles med ablasjon av arytmogene foci under samme inngrep. Sinusrytmen gjenopprettes hos de fleste på kort sikt, men langtidsresultatene er mer usikre. I denne studien, som er en del av den internasjonale CURE-AF-studien, evalueres resultater etter Cox-maze IV-operasjon for atrieflimmer i Norge ved oppfølging etter seks år. MATERIALE OG METODE 19 pasienter inngikk i denne prospektive kohortstudien. Atrieflimmer hadde vart i 40 måneder i gruppen med langvarig persisterende atrieflimmer (n = 12) og 6 måneder i gruppen med persisterende atrieflimmer (n = 7). Operasjon for atrieflimmer ble utført etter Cox-maze IV-prosedyren i CURE-AF-protokollen. De første 12 månedene var oppfølgingen strikt etter CURE-AF-protokoll, deretter var oppfølgingen i primærhelsetjenesten. RESULTATER Sinusrytme var reetablert hos 11 pasienter ved utskrivning og hos 14 pasienter seks måneder postoperativt. Ved oppfølging etter 5–6 år hadde alle pasienter med langvarig persisterende atrieflimmer fått residiv. To av disse fikk sinusrytme etter elektrokonvertering. Seks av syv i gruppen med persisterende atrieflimmer hadde sinusrytme etter 5–6 år. FORTOLKNING Initialt var resultatene gode, med retablering av sinusrytme hos over ⅔ av pasientene etter 6–9 måneder. Fem år senere ble det påvist høy residivfrekvens hos pasienter med langvarig persisterende atrieflimmer. Flere residiv var ikke blitt oppdaget eller forsøkt behandlet av helsevesenet