Cheyne-Stokes respiration in congestive heart failure.

Cheyne-Stokes respiration is an abnormal breathing pattern which commonly occurs in patients with decompensated congestive heart failure and neurologic diseases, in whom periods of tachypnea and hyperpnea alternate with periods of apnea. In the majority of these patients, the ventilatory patterns may not be recognized, and the clinical features are generally dominated by the underlying disease process. Cheyne-Stokes respiration may, however, have profound effects on the cardiopulmonary system, causing oxygen desaturation, cardiac arrhythmias, and changes in mental status. Treatment of Cheyne-Stokes respiration in congestive heart failure with supplemental oxygen or nasal continuous positive airway pressure, in addition to conventional therapy, may improve the overall cardiac function and perhaps the patient's prognosis.     

Cheyne-Stokes respiration in patients hospitalised for heart failure

BackgroundPrevious studies showing a strong relationship between Cheyne-Stokes respiration and the severity of left ventricular systolic dysfunction have usually been done in selected patient populations with lower age and a higher proportion of males than the "typical" in-hospital patient with heart failure. The purpose of the present study was test the strength of this relationship in unselected patients admitted to hospital due to decompensated chronic heart failure.MethodsWe evaluated 191 patients (32% women), mean age 73 years, ready for discharge from the heart failure unit in the University Hospital of Malmö, Sweden. The patients underwent echocardiography for determination of left ventricular ejection fraction and left ventricular inner diastolic diameter. A respiratory investigation during sleep was performed the last night before discharge.ResultsWe found that 66% of the patients had Cheyne-Stokes respiration more than 10% of the total recording time. Only 7 (3.6%) of the patients had predominantly obstructive apnoeas. There was a significant but very weak relationship between left ventricular ejection fraction and left ventricular inner diastolic diameter on one hand and Cheyne-Stokes respiration on the other. Age was a stronger determinant of Cheyne-Stokes respiration than any of the cardiac or other clinical variables.ConclusionAlthough presence of Cheyne-Stokes respiration indicates left ventricular dysfunction, its severity seems only weakly related to the severity of heart failure. Age was found to be a stronger determinant, which may reflect the underlying age-dependency found also in healthy subjects. Due to age restrictions or other selection criteria, the importance of age may have been underestimated in many previous studies on factors associated with Cheyne-Stokes respiration.     

Roles of the AV junction in determining the ventricular response to atrial fibrillation.

The statistical properties of RR interval sequences during cholinergic atrial fibrillation were studied in anesthetized dogs both in control conditions and after the selective injection of dromotropic agents into the atrioventricular (AV) node artery. It was observed that RR interval histogram configurations depended mainly on the mean heart rate, regardless of whether it was a control or a post-injection sequence. The sequences were found to vary from almost regular at fast rates to highly irregular at slow rates, covering all intermediate possibilities. Since the injections of dromotropic agents into the AV node artery were carried out during sinus rhythm between the episodes of fibrillation, their influences on the AV junction, as reflected both on the length of the PR interval during sinus rhythm and on the RR interval dispersion during fibrillation, could be compared. The dispersion of RR intervals was found to increase as the PR interval duration became longer. In addition, it was observed that the generally random character of the RR interval sequences during fibrillation was not affected by the injection of dromotropic agents into the AV node artery. These results were interpreted as an indication that, for a well-established atrial fibrillation, the degree of ventricular irregularity (dispersion of RR intervals) is related to the conductivity within the AV junction and that the random character of RR interval sequences is related to the atrial fibrillatory activity itself.     

Efficacy and safety of atrial fibrillation ablation in heart failure patients with left ventricular ejection fraction less than 50%

IntroductionThe efficacy of catheter ablation in patients with low cardiac function has been previously reported; however, only a few studies have included mid-range ejection fraction (mrEF). This study aimed to evaluate the efficacy and safety of atrial fibrillation (AF) ablation in patients with left ventricular ejection fraction (LVEF) < 50%.MethodsThis study retrospectively analyzed 79 patients (reduced ejection fraction [rEF]/mrEF, 38/41; paroxysmal/persistent, 37/42; heart failure hospitalizations within one year before ablation, 36 [45.6%]) who underwent the first ablation procedure at our hospital from April 2017 to December 2021. Radiofrequency ablation and cryoablation were performed for 69 and 10 patients, respectively.ResultsComplications included pacemaker implantation for postoperative sick sinus syndrome in one patient and inguinal hematoma in one patient. Regarding efficacy, there were significant postoperative improvements in echocardiographic data, blood test values, and diuretic use. After a mean follow-up of 60 months, 86.1% patients had no AF recurrence. There were 9 heart failure hospitalizations (11.4%) and 5 all-cause deaths (6.3%); no significant differences were found between the rEF and mrEF groups. No significant predictors of AF recurrence were found in preoperative patient characteristics.ConclusionAF ablation in patients with LVEF <50% significantly improved cardiac and renal functions with few complications, resulting in a high non-recurrence rate and reduced heart failure.     

Eicosapentaenoic acid prevents atrial fibrillation associated with heart failure in a rabbit model

Atrial fibrillation (AF) is associated with morbidity and mortality of heart failure. Eicosapentaenoic acid (EPA), which is contained in fish oil, was shown to reduce the risk of cardiovascular diseases. We investigated the effects of EPA on AF associated with heart failure in a rabbit model. Rabbits were subjected to ventricular tachypacing (VTP) for 4 wk with or without EPA treatment. Continuous VTP induced heart failure status in these rabbits. The duration of AF (DAF) induced by burst pacing was analyzed by electrophysiological studies. VTP resulted in increased DAF following burst pacing. EPA treatment attenuated increased DAF. Atrial fibrosis increased in response to VTP, accompanied by extracellular signal-regulated kinase (ERK) phosphorylation and transforming growth factor-β1 (TGF-β1) expression in the atrium. Treatment with EPA attenuated atrial fibrosis, ERK phosphorylation, and TGF-β1 expression in response to VTP. EPA treatment increased adiponectin as an anti-inflammatory adipokine and decreased tumor necrosis factor-α as a proinflammatory adipokine in the atrium and epicardial adipose tissues. EPA attenuated VTP-induced AF promotion and atrial remodeling, which was accompanied by modulating the profiles of adipokine production from epicardial adipose tissue. EPA may be useful for prevention and treatment of AF associated with heart failure.     

Normal distribution of ventricular pressure-volume area of arrhythmic beats under atrial fibrillation in canine heart

We previously found the frequency distribution of the left ventricular (LV) effective afterload elastance (E(a)) of arrhythmic beats to be nonnormal or non-Gaussian in contrast to the normal distribution of the LV end-systolic elastance (E(max)) in canine in situ LVs during electrically induced atrial fibrillation (AF). These two mechanical variables determine the total mechanical energy [systolic pressure-volume area (PVA)] generated by LV contraction when the LV end-diastolic volume is given on a per-beat basis. PVA and E(max) are the two key determinants of the LV O(2) consumption per beat. In the present study, we analyzed the frequency distribution of PVA during AF by its chi(2), significance level, skewness, and kurtosis and compared them with those of other major cardiodynamic variables including E(a) and E(max). We assumed the volume intercept (V(0)) of the end-systolic pressure-volume relation needed for E(max) determination to be stable during arrhythmia. We found that PVA distributed much more normally than E(a) and slightly more so than E(max) during AF. We compared the chi(2), significance level, skewness, and kurtosis of all the complex terms of the PVA formula. We found that the complexity of the PVA formula attenuated the effect of the considerably nonnormal distribution of E(a) on the distribution of PVA along the central limit theorem. We conclude that mean (SD) of PVA can reliably characterize the distribution of PVA of arrhythmic beats during AF, at least in canine hearts.     

Mathematical modeling of ventricular disturbances following atrial fibrillation

The present study presents the results of mathematical and computer modeling of atrial fibrillation and ventricular disturbances following atrial fibrillation. The model is based on the assumption that electric impulsation arriving on the atrioventricular node during atrial fibrillation is sum of N independent pulse streams with various amplitude-frequency and phase characteristics. With this model it becomes possible to investigate the dependence of nonlinear dynamics of PP and RR intervals on amplitude-frequency and phase characteristics pulse streams. Results of computer experiments are compared with real physiological experiments on rabbits. Identification of model was carried out by means of least-squares procedure.     

Mathematical modeling of ventricular disturbances following atrial fibrillation

The present study presents the results of mathematical and computer modeling of atrial fibrillation and ventricular disturbances following atrial fibrillation. The model is based on the assumption, that electric impulsation arriving on the atrioventricular node during atrial fibrillation is sum N of independent pulse streams with various amplitude-frequency and phase characteristics. With this model it becomes possible to investigate the dependence of nonlinear dynamics of PP and RR intervals on amplitude-frequency and phase characteristics pulse streams. Results of computer experiments are compared with real physiological experiments on rabbits. Identification of model was carried out by means of least-squares procedure.     

ABC of atrial fibrillation. Antithrombotic treatment for atrial fibrillation.

Antithrombotic prophylaxis with long term warfarin or aspirin reduces thromboembolic risk in atrial fibrillation. Identification, risk assessment, and regular review of all patients with atrial fibrillation should be routine in general and hospital practice. Risk stratification is easily performed on clinical grounds--echocardiography may refine it.     

Transitions in human atrial and ventricular myosin light-chain isoenzymes in response to cardiac-pressure-overload-induced hypertrophy.

1. The light-chain subunits of human atrial and ventricular cardiac muscle were examined by two-dimensional polyacrylamide-gel electrophoresis and limited proteolytic digestion. The light-chain patterns in the normal right and left atria were identical. 2. Myosin preparations isolated from right or left atria that had been subjected to cardiac-pressure-overload-induced hypertrophy also contained ventricular light-chain subunits. These were identified by peptide mapping in sodium dodecyl sulphate. 3. Ventricular light chain-2 was the major species in hypertrophied atria, although light chain-1 subsequently appeared in severe pressure-overload-hypertrophied cases. Evidence is presented for the existence of more than one form of ventricular light chain-2. 4. The transition from atrial to ventricular myosin light chains correlated with the degree of pressure-overload hypertrophy in 83 examples of surgically excised atria. 5. The adult atrial light chain-1 was shown to be homologous to the human foetal ventricular light chain-1 [Price, Littler & Cummins (1980) Biochem. J. 191, 571-580] by peptide mapping. 6. A scheme of atrial/ventricular myosin light-chain isoenzyme transitions is discussed in relation to changing contractile properties in cardiac muscle, together with implications for the role of light-chain subunits.     

Systematic nocturnal atrial demand pacing results in high-output heart failure.

Beat-to-beat parameters of heart rate (HR), intra-arterial blood pressure (BP), central venous pressure, and derived indexes of cardiac output and total peripheral resistance were recorded 18 h/day (from 1800 to 1200 h the following day) in four monkeys (Macaca mulatta) during 20 control days followed by 20 days of atrial demand pacing. The pacing rate was set at approximately 10 beats/min above the fastest hourly average HR recorded during the control period, i.e., sufficient to prevent the normal nocturnal fall in HR. Nocturnal pacing resulted in progressive weekly increases in central venous BP and arterial BP. Analyses of levels and diurnal trends in hemodynamic parameters and cardiac function curves across consecutive 5-day periods of nocturnal pacing revealed a hemodynamic pattern characteristic of high-output heart failure, which progressively increased (week by week) during the early morning hours (0500-0700). Sustained elevated left ventricular work resulting from the prevention of a nocturnal fall in HR may have been responsible for the reduction in cardiac function seen in this experimental model.