Effects of Dexmedetomidine on Basic Cardiac Electrophysiology in Adults; a Descriptive Review and a Prospective Case Study.

Dexmedetomidine (DEX) is a commonly used sedative agent with no or minimal effects on breathing. DEX may also be beneficial in myocardial protection. Since the mechanisms of cardiac effects are not well known, we carried out a descriptive review and examined the effects of DEX on myocardial electrical conduction in a prospective and controlled manner. For the review, clinical studies exploring DEX in myocardial protection published between 2020-2022 were explored. A case study included 11 consecutive patients at a median (range) age of 48 (38-59), scheduled for elective radiofrequency ablation of paroxysmal atrial fibrillation. A bolus dose of DEX 1 µg/kg given in 15 min was followed by a continuous infusion of 0.2-0.7 µg/kg/h. Direct intracardiac electrophysiologic measurements, hemodynamics and oxygenation were measured before and after the DEX bolus. Experimental studies show that DEX protects the heart both via stabilizing cardiac electrophysiology and reducing apoptosis and autophagy after cell injury. The clinical evidence shows that DEX provides cardiac protection during different surgeries. In a clinical study, DEX increased the corrected sinus node recovery time, prolongated the atrioventricular (AV) nodal refractory period and cycle length producing AV nodal Wenckebach retrograde conduction block. DEX has a putative role in organ protection against hypoxic, oxidative and reperfusion injury. DEX slows down the firing of the sinus node and prolongs AV refractoriness.

Timing of pacemaker and ICD implantation in LMNA mutation carriers.

AIMS: LMNA-cardiomyopathy is often associated with pathology in the cardiac conduction system necessitating device implantations. The aim was to study the timing and types of device implantations and need for re-implantations in LMNA mutation carriers. METHODS: We studied the hospital records of 60 LMNA mutation carriers concerning device implantations and re-implantations and their indications. Data were collected until April 2019. RESULTS: The median follow-up time from the first ECG recording to the last clinical follow-up, transplantation, or death was 7.7 (IQR=9.1) years. Altogether 61.7% (n=37) of the LMNA mutation carriers received a pacemaker or an implantable cardioverter defibrillator (ICD), and of them 27.0% (n=10) needed a device upgrade. Notably, in some patients the upgrade took place very soon after the first implantation. The first device was implanted at an average age of 47.9 years (SD=9.5), whereas the upgrade took place at an average age of 50.3 years (SD=8.1). Most upgrades were ICD implantations. Male patients underwent device upgrade more often and at a younger age than women. By the end of follow-up, 35.0% (n=21) of the patients fulfilled echocardiographic criteria for dilated cardiomyopathy, and 90.5% of them (n=19) needed pacemaker implantation. CONCLUSION: Most LMNA mutation carriers underwent pacemaker implantation in this study. Due to the progressive nature of LMNA-cardiomyopathy, device upgrades are quite common. An ICD should be considered when the initial device implantation is planned in an LMNA mutation carrier.

Noninvasive mapping reveals recurrent and suddenly changing patterns in atrial fibrillation-a magnetocardiographic study.

OBJECTIVE: To study noninvasive magnetocardiographic (MCG) mapping of ongoing atrial fibrillation (AF) and, for the possible mapping patterns observed, to develop simplified but meaningful descriptors or parameters, providing a possible basis for future research and clinical use of the mappings. APPROACH: MCG mapping with simultaneous ECG was recorded during arrhythmia in patients representing a range of typical, clinically classical atrial arrhythmias. The recordings were assessed using MCG map animations, and a method to compute magnetic field map orientation (MFO) and its time course was created to facilitate presentation of the findings. All the data were segmented into four categories of ECG waveform regularity. MAIN RESULTS: In visual observation of the MCG animations, an abundance of clear spatial and temporal patterns with regularity were found, often perceived as rotations of the map. This rotation and its sudden reversals of direction were distinctly present in the time course of the MFO. The shortest segments with consistent rotation lasted for some hundreds of milliseconds, i.e. a couple of cycles, but segments lasting for tens of seconds were observed as well. In the ECG, all four categories of regularity were present. The rotation of the MFO was observed in all patients under study and regardless of the ECG categories. Further, a change in ECG category during a measurement was frequently, but not always, found to be simultaneous with a change in the rotation pattern of the MFO. Utilization of spatial information of MCG mapping could enable detection of both regularities and instantaneous phenomena during AF. SIGNIFICANCE: Cardiac mapping may offer a useful noninvasive means to study the mechanisms of AF, including superior temporal resolution.

[Update on current care guideline: atrial fibrillation]. / Eteisvärinä.

The prevalence and incidence of atrial fibrillation (AF) are increasing rapidly. Key recommendations in management of AF include prompt administration of oral anticoagulation to all patients with elevated risk of thromboembolic complications, proper use of antiarrhythmic drugs and invasive therapies in highly symptomatic patients and adequate rate control in patients with permanent AF. The selection between warfarin and the novel oral anticoagulants (apixaban, dabigatran, rivaroxaban) is based on careful evaluation of the benefits and disadvantages of the drugs in a given patient.

[Flatus gone astray and other causes of syncope ]. / Eksynyt pieru ja muita synkopeen syitä.

Loss of consciousness i.e. syncope is a common cause of getting to emergency call service. We describe two patients, in whom fainting was caused by reflexogenic syncope. The diagnosis is quickly solved if there is patience to review the patient history as thoroughly as possible. Registration of the conventional 12-lead electrocardiography and clinical examination usually suffice as basic investigations, without the need for expensive equipment. Careful scrutiny of the medical history will not only reveal the cause of fainting but also the predisposing factors, whereby recurrence of the event can easily be avoided by recognizing a threatening situation early enough.

[Sudden cardiac death in athletes]. / Urheilijoiden sydänperäiset äkkikuolemat.

Sudden deaths occurring during exercise are rare and are most commonly due to cardiac arrest. It is most commonly underlain by symptomless cardiomyopathy or coronary artery disease. Preventive work comes up against a diagnostic problem in distinguishing adaptational changes of the athletic heart from a heart disorder. To reveal the danger of cardiac arrest and reduce human tragedies international sports organizations and cardiologic expert groups recommend screening of cardiac disorders among competing athletes.

[Cryoablation in the treatment of cardiac arrhythmias]. / Kryoablaatio rytmihäiriöiden hoidossa.

Catheter ablation is currently the preferred treatment for various arrhythmias. Radiofrequency ablation has been shown to be efficacious and safe. Cryoablation provides better ablation catheter stability and reduces the risk of an inadvertent atrioventricular (AV) block when treating arrhythmia substrates near the normal conduction system. In our own seven year experience of cryoablation in 157 patients no serious complications occurred. In children and young patients, cryoablation has become the preferred method for AV nodal re-entrant tachycardia. Cryoablation is preferable for all tachycardia substrates near the normal conduction system in children, teenagers and adults.

[Electrophysiological testing of the heart]. / Sydämen elektrofysiologinen tutkimus.

Referral to electrophysiological testing is based on anamnesis and arrhythmic ECG recording. In this study, flexible thin diagnostic catheters are introduced into the patient's heart and by pacing the heart from the atria and ventricles the properties of the heart's intrinsic conducting pathways are determined, as well as whether the patient has potentially treatable structures (substrates) causing arrhythmias. The aim of the study is to initiate an arrhythmia similar to that having caused the patient to seek medical examination. The arrhythmia can often be simultaneously treated with catether ablation.

Interatrial conduction in patients with paroxysmal atrial fibrillation and in healthy subjects.

BACKGROUND: Altered atrial conduction is linked to susceptibility to atrial fibrillation (AF). Whether signal propagation to left atrium (LA) during sinus rhythm differs between patients with paroxysmal lone AF and healthy subjects is not known. METHODS: In 107 patients with lone paroxysmal AF (age 45±12 years) and 94 controls 99-channel magnetocardiography (MCG) was recorded over anterior chest. The duration of the atrial wave (Pd) and the MCG maps over time intervals corresponding to early and later LA activations were determined. Based on magnetic field orientations in LA maps, MCG atrial waves were classified into 3 types which are related to distinct interatrial conduction routes: Type 1 to Bachmann bundle, Type 2 to margin of fossa ovalis or multisite, and Type 3 to coronary sinus ostial connections. RESULTS: Pd was longer in AF patients than in controls (112±13 vs. 104±13; p<0.001), which was most obvious in Type 1 wave (109±12 vs. 102±11 ms, p=0.003). The distribution of the atrial wave types differed between AF patients and controls: Type 1 occurred in 67% and Type 2 in 20% of controls whereas Type 1 occurred in 54% and Type 2 in 42% of AF patients, p<0.01 for difference. CONCLUSIONS: Susceptibility to paroxysmal lone AF is associated with propagation of atrial signal to LA via margin of fossa ovalis or multiple pathways. When conduction occurs via Bachmann bundle, it is related with prolonged atrial activation. Thus altered and alternative conduction pathways may contribute to pathogenesis of lone AF.

Reversal of atrial remodeling after cardioversion of persistent atrial fibrillation measured with magnetocardiography.

BACKGROUND: Atrial fibrillation (AF) causes electrical, functional, and structural changes in the atria. We examined electrophysiologic remodeling caused by AF and its reversal noninvasively by applying a new atrial signal analysis based on magnetocardiography (MCG). METHODS: In 26 patients with persistent AF, MCG, signal-averaged electrocardiography (SAECG), and echocardiography were performed immediately after electrical cardioversion (CV), and repeated after 1 month in 15 patients who remained in sinus rhythm (SR). Twenty-four matched subjects without history of AF served as controls. P-wave duration (Pd) and dispersion (standard deviation of Pd values in individual channels) and root mean square amplitudes of the P wave over the last 40 ms portions (RMS40) were determined. RESULTS: In MCG Pd was longer (122.8 +/- 18.2 ms vs 101.5 +/- 14.6 ms, P < 0.01) and RMS40 was higher (60.4 +/- 28.2 vs 46.9 +/- 19.1 fT) in AF patients immediately after CV as compared to the controls. In SAECG Pd dispersion was increased in AF patients. Mitral A-wave velocity and left atrial (LA) contraction were decreased and LA diameter was increased (all P < 0.01). After 1 month, Pd in MCG still remained longer and LA diameter greater (both P < 0.05), while RMS40 in MCG, Pd dispersion in SAECG, mitral A-wave velocity, and LA contraction were recovered. CONCLUSIONS: Magnetocardiographically detected atrial electrophysiologic alterations in persistent AF diminish rapidly although incompletely during maintained SR after CV. This might be related to the known early high and late lower, but still existent tendency to AF relapses.

Non-invasive detection of conduction pathways to left atrium using magnetocardiography: validation by intra-cardiac electroanatomic mapping.

AIMS: Alteration in conduction from right to left atrium (LA) is linked to susceptibility to atrial fibrillation (AF). We examined whether different inter-atrial conduction pathways can be identified non-invasively by magnetocardiographic mapping (MCG). METHODS AND RESULTS: In 27 patients undergoing catheter ablation of paroxysmal AF, LA activation sequence was determined during sinus rhythm using invasive electroanatomic mapping. Before this, 99-channel magnetocardiography was recorded over anterior chest. The orientation of the magnetic fields during the early (40-70 ms from P onset) and later part (last 50%) of LA depolarization was determined using pseudocurrent conversion. Breakthrough of electrical activation to LA occurred through Bachmann bundle (BB) in 14, margin of fossa ovalis (FO) in 3, coronary sinus ostial region (CS) in 2, and their combinations in 10 cases by invasive reference in total of 29 different P-waves. Based on the combination of pseudocurrent angles over early and late parts of LA activation, the MCG maps were divided to three types. These types correctly identified the LA breakthrough sites to BB, CS, FO, or their combinations in 27 of 29 (93%) cases. CONCLUSION: Magnetocardiographic mapping seems capable of distinguishing inter-atrial conduction pathways. Recognizing the inter-atrial conduction pattern may assist in understanding the pathogenesis of AF and identifying the subgroups for patient-tailored therapy.

Arrhythmias and heart rate variability during and after therapeutic hypothermia for cardiac arrest.

OBJECTIVE: To evaluate the effects of therapeutic hypothermia (HT) of 33 degrees C after cardiac arrest (CA) on cardiac arrhythmias, heart rate variability (HRV), and their prognostic value. DESIGN: Prospective, comparative substudy of a randomized controlled trial of mild HT after out-of-hospital CA, the European Hypothermia After Cardiac Arrest study. SETTING: Intensive care unit of a tertiary referral hospital (Helsinki University Hospital). PATIENTS: Seventy consecutive adult patients resuscitated from out-of-hospital ventricular fibrillation were randomly assigned either to therapeutic HT of 33 degrees C or normothermia. INTERVENTIONS: Patients randomized to HT were cooled with an external cooling device for 24 hours and then allowed to rewarm slowly during 12 hours. In the normothermia group, the core temperature was kept <38 degrees C by antipyretics and physical means. All patients received standard intensive care for at least 2 days. MEASUREMENTS AND MAIN RESULTS: Twenty-four hour ambulatory electrocardiography recordings were performed at 0-24 hours, at 24-48 hours, and at 14 days. The clinical outcome was assessed at 6 months after CA. The occurrence of premature ventricular beats was increased in the HT-treated group during the first two recordings, with no difference in the number of ventricular tachycardia or ventricular fibrillation episodes. All HRV values were significantly higher during the HT (p < 0.01), but no differences were observed 2 weeks later. In multivariate analysis, only shorter delay to restoration of spontaneous circulation (p = 0.009) and the sd of individual normal-to-normal intervals >100 msec of the 24-48-hour recording in the HT group (p = 0.018) predicted good outcome. CONCLUSIONS: The use of therapeutic HT of 33 degrees C for 24 hours after CA was not associated with an increase in clinically significant arrhythmias. Preserved 24 to 48-hour HRV may be a predictor of favorable outcome in patients with CA treated with HT.

Transcardiac gradients of N-terminal B-type natriuretic peptide in aortic valve stenosis.

BACKGROUND: Plasma B-type natriuretic peptide (BNP), as well as the N-terminal part of the prohormone (Nt-BNP), are frequently elevated in aortic valve stenosis (AS). Yet, their release from the heart into the circulation has never been directly studied in AS. AIM: To assess the release of Nt-BNP in AS with focus on the identification of its main determinants. METHODS: We studied 49 adult patients undergoing preoperative cardiac catheterization for isolated AS. Blood was sampled from the aortic root and the coronary sinus for Nt-BNP determination by immunoassay. RESULTS: The mean (+/-S.E.) transcardiac Nt-BNP step-up averaged 79+/-53 pmol/l in 11 control patients free of structural heart disease, 75+/-32 pmol/l in 31 AS patients free of heart failure (HF), 236+/-62 pmol/l in 8 AS patients with diastolic HF (ejection fraction > or = 50%, pulmonary wedge pressure > 14 mm Hg) and 469+/-66 pmol/l in 7 AS patients with systolic HF (ejection fraction < 50%, wedge pressure > 14 mm Hg) (p<0.001). The transcardiac Nt-BNP gradient was independently associated with left ventricular (LV) end-diastolic pressure (beta=0.47, p<0.001) and ejection fraction (beta=-0.29, p<0.019) and with co-existent coronary artery disease (beta=0.23, p=0.050). CONCLUSION: LV diastolic and systolic dysfunction along with coronary artery disease are likely to be the key determinants of cardiac Nt-BNP release in AS. The transcardiac Nt-BNP gradient increases on average three-fold with the development of diastolic HF and six-fold in systolic HF.

Atrial refractoriness and action potential duration after sudden reversal of atrioventricular sequence.

To address the potential of atrioventricular (AV) asynchrony to provoke cardiac arrhythmias, atrial electrophysiology was examined during normal and reversed AV interval in anesthetized pigs. A new automatic stimulation technique was adapted to monitor rapid changes in the effective refractory period (ERP), using continuous AV sequential pacing, incremental extrastimulus interval scanning, and automatic detection of capture. Right atrial ERP using 2-8 ms stimulus interval increments and right atrial and ventricular monophasic action potential (MAP) duration were determined simultaneously when the AV interval was changed from normal (+80 ms) to reversed (-40 ms) and back. During reversed AV interval the peak right atrial pressure increased from 8 +/- 3 to 14 +/- 4 mmHg (P < 0.001) and mean arterial pressure decreased from 86 +/- 18 to 65 +/- 21 mmHg (P < 0.001). At new steady state, atrial ERP and MAP duration at 90% level of repolarization were lengthened by 22 +/- 16 and 42 +/- 12 ms respectively (P < 0.001). Ventricular MAP duration did not change. A statistically significant lengthening in atrial ERP could be demonstrated in 5-10 seconds. After reversion of the AV sequence, the ratio of atrial ERP to MAP duration decreased from 1.27 to 0.94 (P < 0.001) on average for 15 seconds, the change being thought to favor reentry. Thus atrial wall stress from contraction during ventricular systole even for a short period of time modifies atrial electrophysiology. Deficient AV synchrony may immediately contribute to the development of atrial arrhythmias.

Detection of rapid changes in ventricular refractoriness in human studies.

Conventional determination of the ventricular effective refractory period (VERP) is unsuitable for detection of rapid fluctuations in the effective refractory period (ERP). A programmed stimulation system was developed that adapts continuous atrioventricular sequential pacing, incremental extrastimulus interval (S1S2) scanning, and automatic detection of extrastimulus capture which is followed by shortening of S1S2 to execute repeated scanning. The accuracy of ERP determination was tested using variable incremental (2 and 4 ms) and decremental (4-16 ms) steps of the S1S2 interval. Based on a mean of 82 determinations in eight patients, the average VERP values stayed at 249.8-251.0 ms except during the highest capture frequency. Standard deviation of ERP values ranged from 1.1 to 2.5 ms on average at the tested incremental and decremental steps. One determination was accomplished within 7.8-15.6 seconds on average. The ability to track changes in ERP was tested by changing the drive cycle length. Time constants for the adaptation rate of VERP and ventricular monophasic action potential duration at a 90% level of repolarization were determined from each test, and were similar, 51 +/- 8 seconds (mean +/- SEM) for ERP and 51 +/- 6 seconds for the action potential duration. Thus, the developed method provides accurate ERP measurements during rapid variation in ventricular refractoriness. It allows studying the recovery of excitability and the action potential duration simultaneously, and would be valuable particularly in pathological conditions and pharmacologic interventions where these electrophysiological variables become dissociated.