Jus Ksela

Multifractality in heartbeat dynamics in patients undergoing beating-heart myocardial revascularization

BACKGROUND The multifractal approach of HRV analysis offers new insight into the mechanisms of autonomic modulation of the diseased hearts and has a potential to depict subtle changes in cardiac autonomic nervous control not revealed by conventional linear and non-linear analyses in various conditions like heart failure or stable angina pectoris. The aim of this study was to employ the multifractality approach in cardiac surgery patients and evaluate the multifractality before and after beating-heart myocardial revascularization (off-pump CABG). METHODS Twenty-four hour Holter recordings were performed pre- and postoperatively in 60 patients undergoing off-pump CABG. Selected conventional time- and frequency-domain linear HRV indices were calculated from the 24h and 5 min ECG segments, and preselected multifractal parameters τ(q=2), τ(q=3), h_top and Δh were determined for daytime (12:00-18:00) and nighttime (00:00-06:00) periods of the ECG recordings using Ivanovs method. Mean differences over time were tested using paired-samples t-test and exact Wilcoxon matched-pairs test. The results are reported as mean ± SD and median with interquartile range. A p value of <0.05 was considered statistically significant. RESULTS All selected conventional linear HRV parameters decreased significantly after off pump CABG (p from <0.001-0.015). Preoperatively, multifractal parameter τ(q=2) was -0.60 ± 0.12 and -0.54 ± 0.12, τ(q=3) -0.52 ± 0.18 and -0.49 ± 0.17, h_top 0.20 ± 0.07 and 0.15 ± 0.07 and Δh 0.31 ± 0.14 and 0.17 ± 0.14 for daytime and nighttime periods, respectively. Postoperatively, τ(q=2) and τ(q=3) were significantly higher for daytime (-0.49 ± 0.15, p<0.001 and -0.43 ± 0.23, p=0.015), whereas h_top and Δh were significantly higher for both daytime and nighttime (0.25 ± 0.07, p<0.001 and 0.19 ± 0.06, p=0.002 for h_top and 0.41 ± 0.20, p=0.003 and 0.31 ± 0.19, p < 0.001 for Δh, respectively). All pre- and postoperative parameters, except τ(q=2) and τ(q=3) preoperatively, were significantly lower for nighttime as compared to daytime periods. CONCLUSIONS A significant breakdown of multifractal complexity and anti-correlation behavior with a significant sympathetic overdrive and a concomitant parasympathetic withdrawal occurs after off-pump CABG. The circadian pattern of multifractality regains its day-night variation in the first week after the surgical procedure.

Assessment of Nonlinear Heart Rate Dynamics after Beating-Heart Revascularization

BACKGROUND Advanced nonlinear methods of measuring heart rate variability (HRV) derived from the mathematics of complex dynamics and fractal geometry have provided new insights into the abnormalities of heart rate behavior in various pathologic conditions. These methods have provided additional prognostic information compared with traditional HRV measures and clearly have complemented the conventional linear methods. Knowledge about the behavior of complex cardiac dynamics indices after different cardiac procedures is very limited, however. We aimed to clarify how nonlinear heart rate dynamics are affected by beating-heart revascularization (off-pump coronary artery bypass graft [CABG] surgery) within the first week after the procedure. METHODS Included in the study were 66 patients who had isolated stable multivessel coronary artery disease and were in normal sinus rhythm. The patients were on chronic beta-blocker therapy and were scheduled for off-pump CABG. We performed 15-minute high-resolution electrocardiographic recordings preoperatively and on the third and seventh postoperative days to assess linear and nonlinear heart rate dynamics. Frequency-domain measurements, detrended fluctuation analysis (DFA) with short-term (<or=11 beats, alpha1) and long-term (>11 beats, alpha2) correlation properties of RR-intervals, and fractal dimension (FD) measurements (average, high, and low) were made. Arrhythmia was monitored preoperatively with 24-hour Holter recordings, postoperatively by continuous monitoring for the first 4 days after the procedure, and subsequently by clinical monitoring; 24-hour Holter recordings were obtained again on the seventh postoperative day. We used the paired-samples Student t test, the Mann-Whitney U test, and the Fisher exact test for statistical analyses. Differences in arrhythmia occurrence before and after the procedure were tested with the Wilcoxon signed rank test and the McNemar test. A P level < .05 was considered statistically significant. RESULTS Values for all frequency-domain parameters decreased significantly after off-pump CABG (P< .001). Values for the alpha1 and high FD parameters decreased significantly after the procedure (P= .028 and .001, respectively), whereas alpha2 increased significantly (P= .023). DFA alpha1 was significantly lower in patients with postoperative atrial fibrillation than in patients remaining in sinus rhythm (mean +/- SD, 0.79+/-0.32 versus 1.13+/-0.45 [P= .003] on the third postoperative day; 0.89+/-0.31 versus 1.22+/-0.34 [P< .001] on the seventh postoperative day), whereas low and average FDs were significantly higher (1.84+/-0.16 versus 1.68+/-0.19 [P= .003] on the third postoperative day and 1.77+/-0.18 versus 1.66+/-0.17 [P= .01] on the seventh postoperative day for the low FD; 1.83+/-0.09 versus 1.76+/-0.10 [P= .011] on the third postoperative day and 1.80+/-0.11 versus 1.73+/-0.10 [P= .014] on the seventh postoperative day for the average FD). The low FD was significantly higher on the third postoperative day in patients with postoperative deterioration of ventricular ectopy than in patients with improved ventricular ectopy (1.74+/-0.17 versus 1.48+/-0.08, [P= .03]). CONCLUSION The decreases in alpha1, average FD, and high FD indicate that a profound decay of cardiac complexity and fractal correlation can be observed after off-pump CABG. Furthermore, a more extensive impairment of nonlinear indices was observed in patients who developed postoperative arrhythmias than in those who remained in stable sinus rhythm. Our findings suggest that the postoperative hyperadrenergic setting acts as a preliminary condition in which both reduced and enhanced vagal activity may predispose patients to arrhythmia, indicating that postoperative rhythm disturbances are an end point associated with divergent autonomic substrates.

Ventricular arrhythmic disturbances and autonomic modulation after beating-heart revascularization in patients with pulmonary normotension.

SummaryBACKGROUND: De-novo ventricular arrhythmias are potentially life-threatening complications after beating-heart revascularization (off-pump CABG). Whether pulmonary hypertension can influence initiation of ventricular arrhythmias through increased sympathetic activity is controversial. In order to determine the influence of pulmonary hypertension on its relative contribution to ventricular arrhythmia, we first had to define the role of cardiac autonomic modulation in patients with pulmonary normotension. We aimed to observe how parameters of linear and nonlinear heart rate variability are changed pre- and postoperatively in patients with pulmonary normotension undergoing off-pump CABG. METHODS: Fifteen-minute ECG recordings were collected before and after off-pump CABG in 54 patients with multivessel coronary artery disease and pulmonary normotension to determine linear (TP, HF, LF, LF:HF ratio) and nonlinear detrended fluctuation analysis (α1, α2) and fractal dimension (average, high and low) parameters of heart rate variability. Arrhythmia was monitored preoperatively in 24-hour Holter recordings and postoperatively by continuous monitoring and clinical assessment. RESULTS: Deterioration from simple (Lown I–II) to complex (Lown III–V) ventricular arrhythmia was observed in 19 patients, and improvement from complex to simple arrhythmia in five patients (P = 0.022). Patients with postoperative deterioration of ventricular arrhythmia had preoperatively significantly lower values of TP, HF and LF (P = 0.024–0.043) and postoperatively significantly higher values on the low fractal dimension index (P = 0.031) than patients with postoperative improvement of arrhythmia. CONCLUSION: Patients experiencing postoperative deterioration of ventricular arrhythmia already have impaired autonomic regulation before surgery. Higher postoperative values on the low fractal dimension index indicate that sympathetic predominance with or without concomitant vagal withdrawal is the underlying neurogenic mechanism contributing to ventricular arrhythmia.

Short- versus long-term ECG recordings for the assessment of non-linear heart rate variability parameters after beating heart myocardial revascularization

Non-linear analyses of heart rate dynamics reveal subtle changes not evident from conventional heart rate variability measures. Traditionally, the information was inferred from 24-hour ECG recordings, making it less suitable for clinical application. Moreover, only few studies have attempted to evaluate the reliability of non-linear analyses in relation to varying proportion of artifacts in tracings. In 67 patients revascularized with beating-heart technique, fractal dimension and detrended fluctuation analyses were obtained from 24-hour Holter and 15-minute high-resolution ECG recordings pre and postoperatively. We found strong correlations of non-linear indices between 24-hour and 15-minute recordings (0.54-0.77, p<0.001), unaffected by proportion of artifacts.

LVAD as a Bridge to Heart Transplantation in a Patient with Left Ventricular Noncompaction Cardiomyopathy and Advanced Heart Failure

Left ventricular noncompaction cardiomyopathy (LVNC) is a rare hereditary cardiomyopathy characterized by the formation of an outer compacted and inner noncompacted layer of the myocardium. The latter is characterized by prominent trabeculations and deep intertrabecular recesses and is functionally inferior to the compacted myocardium. As there is no specific treatment for patients with LVNC who develop heart failure, the management of these patients is limited and many patients progress to advanced stages of the disease. For LVNC patients with advanced heart failure, the data regarding the use of mechanical circulatory support are scarce. We report a case of a 29-year-old patient with LVNC and advanced refractory heart failure, who was successfully bridged to heart transplantation using a long-term continuous-flow left ventricular assist device.

Use of a Totally Artificial Heart for a Complex Postinfarction Ventricular Septal Defect

The incidence of cardiac rupture complicating myocardial infarction has declined since the introduction of thrombolytic therapy. Despite the advances in the management of myocardial infarction, cardiac rupture remains an important cause of death among infarction-related fatalities. We discuss a patient who presented to our hospital with myocardial infarction and who subsequently developed a complex ventricular septal rupture, for which surgical repair was not feasible. Implantation of a CardioWest Total Artificial Heart (SynCardia Systems) allowed for immediate hemodynamic stabilization and served as a bridge to transplantation.

Right Ventricular Perforation by a Defibrillator Lead Migrating to the Left Breast

Cardiac perforation after an ICD implantation is a rare complication, with a reported incidence between 0.6-5.2%. Its manifestation might be acute, subacute, or delayed, with an acute perforation occurring within the first 24 hours after implantation, frequently accompanied by severe clinical signs, while subacute and delayed perforations have a more benign progression. Here, we report a case of a 69-year old patient with an acute right ventricular perforation by a defibrillator lead migrating all the way through the pericardium and thoracic wall into the left breast, with an unusually mild and benign clinical course, delaying prompt diagnosis and postponing subsequent surgical treatment. Heart perforation with a defibrillator electrode is a rare but dangerous complication, which may lead to pacing failure, cardiac tamponade, cardiogenic shock, and even death. Even with a benign clinical course, one must think of cardiac wall perforation at any time after device implantation, and a contrast enhanced computer tomography (CTA) must be performed if perforation is suspected. At re-implantation, the lead should be located at a different anatomical position within the RV, preferably at the interventricular septal site, and manipulation of the injury site within the RV avoided.

Prolonged circulatory support with short‐term continuous‐flow pump in an infant with end‐stage heart failure

Dear Editors, We report a case of an infant who was successfully supported with Levitronix PediVAS (Levitronix LLC, Waltham, MA) short-term continuous-flow (STCF) pump in both left ventricular assist device (LVAD) and extracorporeal membrane oxygenation (ECMO) settings for 130 consecutive days before he successfully underwent heart transplantation. Mechanical circulatory support (MCS) therapy in infants and small children with endstage heart failure remains an ongoing clinical challenge because of limited number of suitable devices and lack of quality data from randomized controlled trials. A male infant was firstly admitted to our institution at the age of 3 weeks for further evaluation and management of dilated cardiomyopathy with signs of left ventricular (LV) failure. Although initially managed with optimal medical therapy, LV systolic function gradually deteriorated in the subsequent months despite high-dose inotropic support and, at the age of 7 months, acute renal failure developed. In the setting of end-stage LV failure and deteriorating end-organ perfusion and with no identifiable cause for cardiomyopathy found during diagnostic work-up, he was listed for heart transplant and the decision was made to proceed with MCS as bridge to transplant. A STCF Levitronix PediVAS pump was used in LVAD setting with left atrial and ascending aortic cannulation using 14 and 12 Fr heparin-coated cannulas, respectively. After 62 days of LVAD support, fulminant mediastinitis urged us to replace the centrally cannulated LVAD circuit with peripheral veno-arterial (VA) ECMO. Again, Levitronix PediVAS pump was used in VA-ECMO setting with right jugular vein and carotid artery cannulation using 14 and 12 Fr heparin-coated cannulas, respectively. Following targeted antibiotic treatment and vacuumassisted closure therapy, signs of inflammation subsided and the sternum was closed in the subsequent weeks. After 68 days of VA-ECMO support, the patient underwent orthotopic heart transplantation. Surgical procedure and the postoperative course were uneventful. Standard triple immunosuppressive therapy was introduced, and the boy was discharged 20 weeks after the surgery. In the fifth year after transplantation, he is clinically stable with no end-organ dysfunction and managed on outpatient basis. In the last decades, conventional pediatric MCS strategy embraced ECMO for short-term and pulsatile VADs for long-term support [1]. However, complications such as multiorgan failure, sepsis, and thromboembolism continue to limit MCS-related survival, especially in children weighing less than 8 kg [2,3]. Alternative support schemes with STCF pumps as long-term VADs have shown potential advantages over other long-term support forms, yet inadequate information is currently available with respect to complication rates and outcomes after prolonged STCF-VAD use[4,5]. Our case demonstrates that STCF pumps, although designed for short-term support, can successfully bridge infants or small children to transplant even if extremely long support time is needed because of notable shortage of available pediatric donor organs. However, additional studies are required to better understand the optimal management strategies and complication profiles in pediatric patients supported with these pumps [1–4].