Temporal changes in left ventricular function after massive sympathetic nervous system activation

Donor Electrocardiogram Associations With Cardiac Dysfunction, Heart Transplant Use, and Survival: The Donor Heart Study

BACKGROUND

Potential organ donors often exhibit abnormalities on electrocardiograms (ECGs) after brain death, but the physiological and prognostic significance of such abnormalities is unknown.

OBJECTIVES

This study sought to characterize the prevalence of ECG abnormalities in a nationwide cohort of potential cardiac donors and their associations with cardiac dysfunction, use for heart transplantation (HT), and recipient outcomes.

METHODS

The Donor Heart Study enrolled 4,333 potential cardiac organ donors at 8 organ procurement organizations across the United States from 2015 to 2020. A blinded expert reviewer interpreted all ECGs, which were obtained once hemodynamic stability was achieved after brain death and were repeated 24 ± 6 hours later. ECG findings were summarized, and their associations with other cardiac diagnostic findings, use for HT, and graft survival were assessed using univariable and multivariable regression.

RESULTS

Initial ECGs were interpretable for 4,136 potential donors. Overall, 64% of ECGs were deemed clinically abnormal, most commonly as a result of a nonspecific St-T-wave abnormality (39%), T-wave inversion (19%), and/or QTc interval >500 ms (17%). Conduction abnormalities, ectopy, pathologic Q waves, and ST-segment elevations were less common (each present in ≤5% of donors) and resolved on repeat ECGs in most cases. Only pathological Q waves were significant predictors of donor heart nonuse (adjusted OR: 0.39; 95% CI: 0.29-0.53), and none were associated with graft survival at 1 year post-HT.

CONCLUSIONS

ECG abnormalities are common in potential heart donors but often resolve on serial testing. Pathologic Q waves are associated with a lower likelihood of use for HT, but they do not portend worse graft survival.

Beta-adrenergic receptor polymorphisms and cardiac graft function in potential organ donors

Prior studies have demonstrated associations between beta-adrenergic receptor (βAR) polymorphisms and left ventricular dysfunction-an important cause of allograft nonutilization for transplantation. We hypothesized that βAR polymorphisms predispose donor hearts to LV dysfunction after brain death. A total of 1043 organ donors managed from 2001-2006 were initially studied. The following βAR single nucleotide polymorphisms were genotyped: β1AR 1165C/G (Arg389Gly), β1AR 145A/G (Ser49Gly), β2AR 46G/A (Gly16Arg) and β2AR 79C/G (Gln27Glu). In multivariable regression analyses, the β2AR46 SNP was significantly associated with LV systolic dysfunction, with each minor allele additively decreasing the odds for LV ejection fraction <50%. The β1AR1165 and β2AR46 SNPs were associated with higher dopamine requirement during the donor management period: donors with the GG and AA genotypes had ORs of 2.64 (95% CI 1.52-4.57) and 2.70 (1.07-2.74) respectively for requiring >10 μg/kg/min of dopamine compared to those with the CC and GG genotypes. However, no significant associations were found between βAR SNPs and cardiac dysfunction in 364 donors managed from 2007-2008, perhaps due to changes in donor management, lack of power in this validation cohort, or the absence of a true association. βAR polymorphisms may be associated with cardiac dysfunction after brain death, but these relationships require further study in independent donor cohorts.

Electrocardiographic characteristics of potential organ donors and associations with cardiac allograft use

BACKGROUND

Current regulations require that all cardiac allograft offers for transplantation must include an interpreted 12-lead electrocardiogram (ECG). However, little is known about the expected ECG findings in potential organ donors or the clinical significance of any identified abnormalities in terms of cardiac allograft function and suitability for transplantation.

METHODS AND RESULTS

A single experienced reviewer interpreted the first ECG obtained after brain stem herniation in 980 potential organ donors managed by the California Transplant Donor Network from 2002 to 2007. ECG abnormalities were summarized, and associations between specific ECG findings and cardiac allograft use for transplantation were studied. ECG abnormalities were present in 51% of all cases reviewed. The most common abnormalities included voltage criteria for left ventricular hypertrophy, prolongation of the corrected QT interval, and repolarization changes (ST/T wave abnormalities). Fifty-seven percent of potential cardiac allografts in this cohort were accepted for transplantation. Left ventricular hypertrophy on ECG was a strong predictor of allograft nonuse. No significant associations were seen among corrected QT interval prolongation, repolarization changes, and allograft use for transplantation after adjusting for donor clinical variables and echocardiographic findings.

CONCLUSIONS

We have performed the first comprehensive study of ECG findings in potential donors for cardiac transplantation. Many of the common ECG abnormalities seen in organ donors may result from the heightened state of sympathetic activation that occurs after brain stem herniation and are not associated with allograft use for transplantation.

Neurocardiogenic injury in neurovascular disorders

cardiac injury occurs frequently after stroke; and the most widely investigated form of neurocardiogenic injury is aneurysmal subarachnoid hemorrhage. Echocardiography and screening for elevated troponin and B-type natriuretic peptide levels may help prognosticate and guide treatment of stroke. Cardiac catheterization is not routinely recommended in subarachnoid hemorrhage patients with left ventricular dysfunction and elevated troponin. The priority should be treatment of the underlying neurologic condition, even in patients with left ventricular dysfunction. Cardiac injury that occurs after subarachnoid hemorrhage appears to be reversible. In contrast to subarachnoid hemorrhage patients, patients with ischemic stroke are more likely to have concomitant significant heart disease. For patients who develop brain death, cardiac evaluation under optimal conditions may help increase the organ donor pool.

Cardiac complications after aneurysmal subarachnoid hemorrhage

BACKGROUND

Cardiac complications are frequently encountered by neurointensivists caring for patients with SAH. Our aim was to better characterize the natural history of various cardiac abnormalities in this population. We sought to determine the risk factors for cardiac abnormalities, patient outcome, and impact of treatment type on cardiac abnormalities.

METHODS

We performed a single center retrospective review of admissions of patients with aneurysmal SAH to the neurosurgical ICU in a large university hospital. Patient demographics, pertinent history, cardiac tests, hospital LOS, intervention type, and discharge outcome were collected.

RESULTS

Data from 266 patients were available for analysis. Of these patients, 50% (n = 133) demonstrated cardiac abnormalities as indicated by abnormal EKG, ECHO, or troponin I. Only age was determined to be an independent statistically significant predictor of cardiac abnormality (P = .01). There was no difference in mortality between the cardiac abnormality and control groups (P = .33). However, there was increased morbidity in the cardiac abnormality group as demonstrated by worse discharge disposition, in addition to increased length of hospital stay (22.6 vs 17.1 days, P < .01). The incidence of cardiac abnormalities was the same among surgical and endovascular treatment groups.

CONCLUSIONS

Cardiac abnormalities, including those that meet ACC criteria for MI, are common among patients with SAH. However, in contrast to cardiac events outside the context of SAH, these abnormalities do not increase mortality. They do, however, adversely affect discharge disposition and prolong hospital LOS. The type of aneurysm treatment does not affect the incidence or outcome of cardiac abnormalities.

Acute neurocardiogenic injury after subarachnoid hemorrhage

BACKGROUND

Left ventricular (LV) systolic dysfunction has been reported in humans with subarachnoid hemorrhage (SAH), and its underlying pathophysiology remains controversial. Possible mechanisms include myocardial ischemia versus excessive catecholamine release from sympathetic nerve terminals.

METHODS AND RESULTS

For 38 months, echocardiography and myocardial scintigraphy with technetium sestamibi (MIBI) and meta-[(123)I]iodobenzylguanidine (MIBG) were performed on 42 patients admitted with SAH to assess myocardial perfusion and sympathetic innervation, respectively. A blinded observer interpreted the scintigraphic images. Cardiac troponin I (cTI) was measured to quantify the degree of myocyte necrosis. Blinded observers calculated the LV ejection fraction and graded each LV segment as normal (score=1), hypokinetic (score=2), or akinetic (score=3). A wall-motion score was calculated by averaging the sum of the 16 segments. All subjects with interpretable scans (N=41) had normal MIBI uptake. Twelve subjects had either global (n=9) or regional (n=3) absence of MIBG uptake. In comparison with patients with normal MIBG uptake, those with evidence of functional denervation were more likely to have LV regional wall-motion abnormalities (92% versus 52%, P=0.030) and cTI levels >1 microg/L (58% versus 21%, P=0.029).

CONCLUSIONS

LV systolic dysfunction in humans with SAH is associated with normal myocardial perfusion and abnormal sympathetic innervation. These findings may be explained by excessive release of norepinephrine from myocardial sympathetic nerves, which could damage both myocytes and nerve terminals.

Hypoglycemia-Induced Neurogenic-Type Pulmonary Edema: An Underrecognized Association

OBJECTIVE

To report a case of hypoglycemia-induced pulmonary edema and to analyze the underlying pathophysiologic processes.

METHODS

A case report with clinical and laboratory data is presented, and related studies from the medical literature are discussed.

RESULTS

A 23-year-old man with type 1 diabetes was brought to the emergency department because he was found unconscious at home. Despite a morning blood glucose level of 30 mg/dL, he had taken his usual dose of Lente insulin (40 U), and a period of unconsciousness of unknown duration ensued. Intravenous administration of dextrose increased his blood glucose level to 118 mg/dL, but x-ray films of the chest disclosed evidence of pulmonary edema. After 48 hours of supportive care, his respiratory signs and symptoms resolved. The pathophysiologic construct for hypoglycemia-induced pulmonary edema is thought to be the same as for neurogenic pulmonary edema, with a massive sympathetic nervous system discharge being the common denominator in both conditions.

CONCLUSION

Clinicians should be aware that severe hypoglycemia can lead to noncardiogenic pulmonary edema as a result of a massive sympathetic nervous system discharge and its associated hemodynamic alterations, in the same manner as occurs in neurogenic pulmonary edema.

Neurogenic cardiac injury

Cardiac injury may occur following many types of brain injury, although the most widely investigated form of neurocardiogenic injury is subarachnoid hemorrhage (SAH). Echocardiography may help prognosticate and aid in the treatment of SAH if left ventricular (LV) dysfunction is suspected or if troponin levels are elevated. Cardiac catheterization, however, is not routinely recommended in SAH patients with LV dysfunction and elevated troponin. The priority should be treatment of the underlying neurological condition, even in the setting of LV dysfunction. Cardiac injury that occurs following an SAH appears to be reversible. For patients that develop brain death cardiac evaluation under optimal conditions may help increase the donor pool.

Non-invasive estimation of cardiac output in critical care patients

OBJECTIVE

This study was carried out to compare cardiac output measurements determined by thermodilution and by Portapres, a non-invasive system.

DESIGN, PATIENTS AND SETTING

Eighty-seven non-invasive blood pressure measurements were performed in 46 patients in our critical care unit utilising the new, non-invasive Portapres system. Cardiac output values were obtained from these blood pressure values using an aortic impedance model and compared to cardiac output values estimated by the thermodilution technique.

MEASUREMENTS AND MAIN RESULTS

Statistically significant (p < 0.01) differences (2.3 l/min; limits of agreement +/-5 l/min) were noted between invasive and non-invasive cardiac output measurements. Differences in measured cardiac outputs increased for patients receiving catecholamine therapy, in patients with hemodynamic instability (e.g., sepsis and cardiac insufficiency), in patients with artificial ventilation, in patients with long duration of intensive care, in younger (<60 yr) patients and in women. We found no influence of the body mass index (BMI) on the accuracy of Portapres results. In only one single subgroup, 10 patients with pulmonary diseases, Portapres measurements were not statistically significant different from reference results.

CONCLUSIONS

To date, Portapres measurements cannot replace thermodilution cardiac output estimations. Fluctuations of finger arterial perfusion due to hemodynamic instability, hypothermia and catecholamines may be responsible for problems of Portapres use in critically ill patients.