Use of Bioimpedance to Assess Changes in Hemodynamics During Acute Administration of CPAP.

BACKGROUND: Attempts to investigate the mechanisms by which continuous positive airway pressure (CPAP) therapy improves heart function in patients with obstructive sleep apnea (OSA) have been limited by the lack of non-invasive methods to assess cardiac performance. We used transthoracic electrical bioimpedance (TEB) to assess acute hemodynamic changes including heart rate (HR), stroke volume (SV), cardiac output (CO) and cardiac index (CI) during PAP titration in (1) post-operative cardiac surgery patients, (2) patients with severe OSA, and (3) normal healthy volunteers. METHODS: Post-operative cardiac surgery patients were studied via TEB and pulmonary artery catheter (PAC) during acute titration of positive end-expiratory pressure (PEEP) while mechanically ventilated. Patients with severe OSA were studied non-invasively by TEB during acute CPAP titration in supine stage 2 sleep, and normal subjects while awake and recumbent. RESULTS: In post-operative cardiac surgery patients (n = 3), increasing PEEP to 18 cmH2O significantly reduced SV and CI relative to baseline. There was no difference between TEB and PAC in terms of ability to assess variations in hemodynamic parameters. In patients with severe OSA (n = 3), CPAP titration to optimal pressure to alleviate obstructive apneas reduced HR, SV, CO and CI significantly compared to without CPAP. In three healthy subjects, maximal tolerated CPAP reduced SV and CO significantly compared to baseline. CONCLUSIONS: Acute administration of CPAP causes a decrease in CO and CI, apparently a consequence of a reduction in SV. TEB appears to be an accurate and reproducible non-invasive method of detecting changes in hemodynamics.

Primary cardiac diffuse large B cell lymphoma presenting with superior vena cava syndrome.

Primary cardiac lymphomas are rare extranodal lymphomas that should be distinguished from secondary cardiac involvement by disseminated non-Hodgkin's lymphoma. Cardiac lymphomas often mimic other cardiac neoplasms, including myxomas and angiosarcomas, and often require multimodality cardiac imaging, in combination with endomyocardial biopsy, excisional biopsy or pericardial fluid cytology, to establish a definitive diagnosis. A 60-year-old immunocompetent man who presented with superior vena cava syndrome secondary to a right atrial, primary cardiac diffuse large B cell lymphoma (non-Hodgkin's lymphoma) is described in the present article. The patient had no clinical evidence of disseminated lymphoma and was successfully treated with prompt surgical excision of his atrial mass, followed by anthracycline-based chemotherapy. The patient required multi-modality cardiac imaging to accurately identify and plan surgical excision of his cardiac lymphoma. The therapeutic management and clinical and radio-logical features of primary cardiac lymphoma are reviewed.

Primary cardiac lymphoma: molecular cytogenetic characterization of a rare entity.

BACKGROUND: The majority of cardiac atrial neoplasms represent benign myxomas. Rarely, malignant cardiac neoplasms are encountered and can include primary cardiac neoplasms, as well as secondary tumors involving the heart. As many cardiac neoplasms lack pathognomonic clinical features, histopathologic diagnosis is crucial for classification and appropriate treatment of these neoplasms. Molecular investigation is critical to begin to catalogue genomic changes that correlate with these malignancies. METHODS: A 60-year-old man presented with superior vena cava syndrome, and computed tomographic scan revealed an infiltrative mass of the right atrium that nearly filled the atrial chamber and partially occluded superior vena cava flow. Urgent surgical resection revealed a soft mass with the appearance of "fish flesh." Histologic, immunochistochemical, cytogenetic, and detailed molecular investigations were carried out. RESULTS: Histologic examination revealed complete replacement of the atrial wall by diffuse sheets of pleomorphic lymphoid cells with occasional smaller plasmacytoid cells. The predominant lymphoid population was immunoreactive for CD45, CD20, CD79a, BCL-2, BCL-6, Ki-67, CD10, p53, and light chain restricted for IgM lambda. A diagnosis of primary cardiac diffuse large B-cell lymphoma with plasmacytoid differentiation was established and was supported by cytogenetic studies demonstrating the presence of a t(14;18)(q32;q21) translocation in addition to other chromosomal abnormalities. Fluorescence in situ hybridization revealed no evidence of a C-MYC translocation. CONCLUSION: In this single case, comparative genomic hybridization analysis using both bacterial artificial chromosome and oligonucleotide arrays correlated well with cytogenetic findings and allows for the cataloguing of more subtle genomic events.

Heart rate variability following coronary artery bypass graft surgery as a function of recovery time, posture, and exercise.

This study examined the claim made by Niemela et al. (1992) that the decline in heart rate variability after coronary artery bypass graft surgery is irreversible. We tested six women and 16 men six and 12 weeks postoperative in three postures: in the supine position, in the standing position, and during low-intensity steady-state exercise. Beat-by-beat arterial blood pressure and electrocardiographic R-R interval data were collected continuously for 10 min in each condition. R-R interval data were analyzed with spectral analysis; baroreflex data were analyzed using the sequence method. Our results show that the indices of parasympathetic modulation improved over time, as seen by an increased spontaneous baroreflex sensitivity and parasympathetic indicator, that both indices were affected by posture, and that spontaneous baroreflex sensitivity was also affected by low-intensity exercise. The effects of posture are consistent with attenuated responses of healthy older subjects to orthostatic stress. Similarly, the effects of low-intensity exercise are consistent with findings in healthy subjects. We found that spontaneous baroreflex sensitivity declined during exercise, whereas, in healthy subjects, this is maintained during low-intensity steady-state exercise. Our results of significant functional recovery between six and 12 weeks postoperative suggest that at least some of the autonomic dysfunction following surgery is temporary. Previously, no such duration of study has lasted longer than four or six weeks following cardiac surgery, which may not have been long enough to show significant functional restoration in heart rate variability.

Spontaneous baroreflex sensitivity after coronary artery bypass graft surgery as a function of gender and age.

The effects of coronary artery bypass graft (CABG) surgery on spontaneous baroreflex (SBR) sensitivity and heart rate variability were examined in 11 women and 23 men preoperatively and 5 days postoperatively. Electrocardiograph R-R interval and beat-by-beat arterial blood pressure data were collected continuously for 20 min in the supine and standing postures. Coarse graining spectral analysis was performed on the heart rate variability data. Spontaneous baroreflex sensitivity declined after surgery with a differential influence of gender. Men showed a decrease in SBR slope following surgery, with a greater decrease in the standing posture; the parasympathetic (PNS) indicator was lower postoperatively and in the standing posture; the reduction in low-frequency (LF) power was greater for the younger men. In women, the PNS indicator was lower in the standing posture. Both men and women showed a decrease in high-frequency power following CABG surgery, which decreased the sensitivity of the short-term cardiac control mechanisms that modulate heart rate, with the greater effects occurring in men. The reduction in SBR sensitivity indicates that the ability of the cardiovascular system to respond rapidly to changing stimuli was compromised. The decline in the PNS indicator implies that patients were vulnerable to the risks of myocardial ischemia, sympathetically mediated cardiac dysrhythmias, and sudden cardiac death.