Long-Term Outcomes of Bovine versus Porcine Mitral Valve Replacement: A Multicenter Analysis

Introduction

Recent national guidelines recommending mitral valve replacement (MVR) for severe secondary mitral regurgitation have resulted in an increased utilization of mitral bioprosthesis. There is a paucity of data on how longitudinal clinical outcomes vary by prosthesis type. We examined long-term survival and risk of reoperation between patients having bovine vs. porcine MVR. Study Design. A retrospective analysis of MVR or MVR + coronary artery bypass graft (CABG) from 2001 to 2017 among seven hospitals reporting to a prospectively maintained clinical registry was conducted. The analytic cohort included 1,284 patients undergoing MVR (801 bovine and 483 porcine). Baseline comorbidities were balanced using 1 : 1 propensity score matching with 432 patients in each group. The primary end point was all-cause mortality. Secondary end points included in-hospital morbidity, 30-day mortality, length of stay, and risk of reoperation.

Results

In the overall cohort, patients receiving porcine valves were more likely to have diabetes (19% bovine vs. 29% porcine; p < 0.001), COPD (20% bovine vs. 27% porcine; p=0.008), dialysis or creatinine >2 mg/dL (4% bovine vs. 7% porcine; p=0.03), and coronary artery disease (65% bovine vs. 77% porcine; p < 0.001). There was no difference in stroke, acute kidney injury, mediastinitis, pneumonia, length of stay, in-hospital morbidity, or 30-day mortality. In the overall cohort, there was a difference in long-term survival (porcine HR 1.17 (95% CI: 1.00-1.37; p=050)). However, there was no difference in reoperation (porcine HR 0.56 (95% CI: 0.23-1.32; p=0.185)). In the propensity-matched cohort, patients were matched on all baseline characteristics. There was no difference in postoperative complications or in-hospital morbidity and 30-day mortality. After 1 : 1 propensity score matching, there was no difference in long-term survival (porcine HR 0.97 (95% CI: 0.81-1.17; p=0.756)) or risk of reoperation (porcine HR 0.54 (95% CI: 0.20-1.47; p=0.225)).

Conclusions

In this multicenter analysis of patients undergoing bioprosthetic MVR, there was no difference in perioperative complications and risk of reoperation of long-term survival after matching.

Magnetic resonance spectroscopy for measuring the biodistribution and in situ in vivo pharmacokinetics of fluorinated compounds: validation using an investigation of liver and heart disposition of tecastemizole

BACKGROUND AND OBJECTIVE

The study of biodistribution and in situ pharmacokinetics is a challenging, but sometimes very important, aspect of premarketing characterization of drugs. We aimed to develop a non-invasive fluorine magnetic resonance (MR) spectroscopic method for the absolute quantitation of a mono-fluorinated compound and of its metabolites in the heart and liver of healthy subjects for this purpose.

METHOD

We used fluorine MR spectroscopy (MRS) at 4 T (Tesla) and external standardization in an open label multiple-dose study. Twenty-three healthy adult subjects were enrolled in the study. The surface coil localized fluorine MR spectrum was monitored in the heart and liver at baseline and after oral administration of multiple doses of tecastemizole. Steady-state measurements were made at set time points that depended upon dose, and washout measurements were made only on subjects in which in vivo fluorine signal was observed.

RESULTS AND DISCUSSION

At 4 T, under the given experimental conditions, the method had a lower limit of quantitation (LLOQ) of about 2.6 microm and a limit of detection (LOD) of about 0.3 microm for solution state samples (linewidth approximately 15 Hz). The measurement reproducibility was 6.4% using a 50 microm phantom. The effect of MR operator and spectral analyst on the calculated calibration curve slope was small, with inter-rater correlation coefficients of 0.999 and 0.998 respectively. MR signal from fluorine-containing tecastemizole-related moieties was observed in situ only at day 8 in the liver of three of five subjects dosed at 270 mg/day. The average in situ concentration was estimated to be 58+/-22 microm, with an average test-retest reproducibility of 216%. Extrapolating the in vitro results to human measurements, with an approximate linewidth of 250 Hz, predicts in situ LOD and LLOQ values of approximately 6 and 44 microm respectively. However, the human study had a fluorine MRS LOD of approximately 20 microm. The decrease in sensitivity and the increase in variability of the in vivo, in situ measurements compared with the validation study most likely arose from coil placement and incomplete rephasing of the MR signal by the respiratory phase compensation method.

CONCLUSION

The measured concentrations were the lowest ever recorded for a multi-dose exogenous mono-fluorinated compound in the human liver using a validated fluorine MR quantitation method. The proposed non-invasive MR method for studying the biodistribution and in situ pharmacokinetics of mono-fluorinated compounds in the liver and heart should have broader application to the development of non-invasive biomarkers.

Biexponential transverse relaxation (T(2)) of the proton MRS creatine resonance in human brain

Differences in proton MRS T(2) values for phosphocreatine (PCr) and creatine (Cr) methyl groups (3.0 ppm) were investigated in studies of phantoms and human brain. Results from phantom studies revealed that T(2) of PCr in solution is significantly shorter than T(2) of Cr. Curve-fitting results indicated that the amplitude-TE curves of the total Cr resonance at 3.0 ppm in human brain (N = 26) fit a biexponential decay model significantly better than a monoexponential decay model (P < 0.006), yielding mean T(2) values of 117 +/- 21 ms and 309 +/- 21 ms. Using a localized, long-TE (272 ms) point-resolved spectroscopy (PRESS) proton MRS during 2 min of photic stimulation (PS), an increase of 12.1% +/- 3.5% in the mean intensity of the total Cr resonance in primary visual cortex (VI) was observed at the end of stimulation (P < 0.021). This increase is consistent with the conversion of 26% of PCr in VI to Cr, which is concordant with (31)P MRS findings reported by other investigators. These results suggest a significantly shorter T(2) for PCr than for Cr in vivo. This difference possibly could be exploited to quantify regional activation in functional spectroscopy studies, and could also lead to inaccuracies in some circumstances when the Cr resonance is used as an internal standard for (1)H MRS studies in vivo.

Multinuclear magnetic resonance spectroscopy studies of brain purines in major depression

OBJECTIVE

Studies of depressed adults have shown abnormalities in cerebral energy metabolism, as noted by low brain levels of nucleoside triphosphate (NTP), which primarily represents adenosine triphosphate (ATP). This study was undertaken to determine whether proton magnetic resonance spectroscopy (1H MRS) measures of the low-field purine resonance, which arises primarily from adenosine phosphates, can be used to assess abnormalities in cerebral purine metabolism in depressed adults.

METHOD

Data from 1H MRS and phosphorus-31 (31P) MRS were acquired for depressed and nondepressed comparison subjects. Intensities of the purine resonance, by 1H MRS (7.5-8.5 ppm), and of NTP, by 31P MRS, were determined.

RESULTS

Purine resonance intensities did not differ on average between depressed patients and comparison subjects. However, purine levels were approximately 30% lower in female depressed subjects who subsequently responded to fluoxetine treatment than in those who did not respond. Beta-NTP was lower by 21% in responders than in nonresponders and was correlated with purine levels for the depressed subjects.

CONCLUSIONS

Brain purine levels are low in female depressed patients who respond to treatment with fluoxetine, suggesting that response to treatment might be predicted by using 1H MRS. These observations also suggest that agents that increase brain adenosine levels may have antidepressant efficacy.

Influence of peripheral nerve stimulation on human motor cortical excitability in patients with ventrolateral thalamic lesion

OBJECTIVE

To determine the peripheral afferent pathways that influence the activities of the motor cortex by examining the effects of peripheral nerve stimulation on motor cortical excitability.

PATIENTS AND METHODS

We examined 12 healthy volunteers and 4 patients with localized brain lesions caused by cerebrovascular attack. Of the 4 patients, 1 patient had pontine infarction, including medial lemniscus, and severe sensory deficit and 3 had small localized lesions in the lateral part of the thalamus and neither sensory impairment nor abnormal N20 waves on somatosensory evoked potential recordings. Central motor tract excitability was examined by measuring a change in the motor evoked potential (MEP), using transcranial magnetic stimulation of the motor cortex after peripheral nerve stimulation at the wrist significantly increased MEP response in the controls at long conditioning-test intervals of 28 to 60 milliseconds, as well as at short intervals of 0 to 6 milliseconds. A late MEP potentiation was not observed on the affected side in all patients.

CONCLUSIONS

The loss of late MEP potentiation in patients with pontine and thalamic lesions indicates that this potentiation is caused by the alternation of the motor cortical excitability. Furthermore, the results in the patients with thalamic lesions suggest that the lateral nuclei of the thalamus, other than the ventral posterolateral nucleus and probably including the ventrolateral nucleus, have an important function in the processing of peripheral sensory input for tuning motor cortical excitability.

Sympathetic skin response in Parkinson's disease

Sudomotor function in 83 patients with Parkinson's disease (PD) was evaluated using the sympathetic skin response (SSR) and sweat response to intradermal acetylcholine (ACh) injection. The incidence of abnormal SSRs (36.1%) increased, and the size of the response decrease with the severity of the illness. Neither the incidence of abnormal SSRs nor the amplitudes of the responses were influenced by levodopa or an anticholinergic agent. The SSR therefore can be used to evaluate the sudomotor efferent pathway in PD patients. In all the patients who had no SSR response, the local sweat response to ACh showed a reduced number of excitable sweat glands and low sweat volume. One patient, whose local sweat response to ACh was markedly impaired, had unmyelinated and acetylcholinesterase-positive fiber densities that were in the normal range in his biopsied sural nerve. The abnormal sweat response to ACh is considered to reflect the dysfunction of postganglionic sympathetic fibers in PD patients.

Dysautonomia with acute sensory motor neuropathy. A new classification of acute autonomic neuropathy

OBJECTIVES

To characterize the dysautonomia associated with acute sensory motor neuropathy and to discuss the classification of acute autonomic neuropathy.

DESIGN

Case series.

METHODS

Sympathetic skin response. Local sweat response to acetylcholine. Norepinephrine infusion test and acetylcholinesterase histochemistry of sural nerve biopsy specimens in addition to making conventional analyses of myelinated and unmyelinated fibers.

RESULTS

In 12 patients with chronic neuropathy, acetylcholinesterase-positive fiber density and plantar sympathetic skin response size were well correlated, but in the two patients with acute autonomic sensory and motor neuropathy, there were discrepancies, acetylcholinesterase-positive fiber density being well preserved and sympathetic skin responses being absent. Histologic and electrophysiologic results indicated primary demyelination of the myelinated fibers. In contrast, previous studies of acute autonomic sensory and motor neuropathy reported dysfunction of the sympathetic postganglionic fibers and axonopathic change in myelinated fibers, poor recovery from dysautonomia.

CONCLUSIONS

Dysautonomia with acute idiopathic neuropathy can be divided into two categories--postganglionic axonopathic and preganglionic demyelinating types of the sympathetic efferent pathways. The recovery from dysautonomia produced by the former lesion is poor, but recovery is better for that produced by the latter lesion.

Increased central motor tract excitability in Creutzfeldt-Jakob disease

Central motor tract excitability was examined in 2 patients with Creutzfeldt-Jakob disease (CJD) and 8 normal subjects by measuring change in the motor evoked potential (MEP) by transcranial magnetic stimulation of the motor cortex after peripheral nerve stimulation. Conditioning stimulation of the median nerve at the wrist greatly increased MEP size (500-1700%) as compared to the size for normal subjects (140-380%) at conditioning-test (C-T) intervals of 30-60 msec for patient 1 and 40-70 msec for patient 2. Moreover, stimulation of the contralateral median nerve at the wrist and of the second and third digits also increased MEP size in the CJD patients; whereas, there was no increase in size in the normals. The time courses of abnormal MEP potentiation were very consistent with the course of the corresponding C reflex. One of the CJD patients had a normal size SEP, and neither patient showed hyperexcitability in SEP-recovery at C-T intervals of 20-60 msec at which there was marked MEP potentiation. These results indicate that there was hyperexcitability of the central motor tract in the CJD patients after the conditioning of muscle and cutaneous peripheral afferents and that it extended to the ipsilateral cortex on the conditioning side as well.

[Sudomotor dysfunction in Parkinson's disease]

Sudomotor function was evaluated by using the sympathetic skin response (SSR) and the sweat response to intradermal acetylcholine (ACh) injection in 69 patients with Parkinson's diseases (PD). The incidence of SSR abnormality (34.8%) was as high as that of orthostatic hypotension (30.4%) and increased with the severity of the illness. Anticholinergic drug did not influence the incidence of SSR abnormality. Therefore, the SSR is useful in evaluating sudomotor efferent pathway in PD patients. Moreover, in all patients, sweat response to ACh showed a reduced number of excitable sweat glands and a low volume of sweat. In a patient in whom sweat response to ACh was markedly impaired, however, the density of acetylcholinesterase-positive unmyelinated fibers in biopsied sural nerve was in normal range. Therefore, this is considered to indicate functional disturbance of the postganglionic sympathetic fibers in PD patients, without morphological changes.

Idiopathic palatal myoclonus

Two cases with idiopathic palatal myoclonus without other neurological deficits were described. They did not have any other neurological deficits other than myoclonus of branchial muscles. In these cases, the myoclonus disappeared during natural or induced sleep. In Case 1, the myoclonus ceased transiently when the patient was calculating or receiving an injection. In Case 2, the myoclonus disappeared with intravenous injection of saline as a placebo. Detailed examinations, including brain CT, MRI and multiple evoked potentials, showed normal results. The myoclonus in Case 2 disappeared after we had explained that her disease was benign. Since the clinical features and laboratory data in idiopathic palatal myoclonus are quite different from those in palatal myoclonus with other neurological deficits, idiopathic palatal myoclonus is considered to be a separate syndrome. Invasive examinations or excessive medications should be avoided because of its benign prognosis.

MRI findings of inferior olives in palatal myoclonus

Four patients with palatal myoclonus (PM) were studied with magnetic resonance imaging (MRI). Increased signal intensity and bilateral enlargement of the inferior olives were recognized in two patients with bilateral PM, pontine haemorrhage and neuro-Behçet disease, and a similar olivary change on the contralateral side was noted in a case of pontine infarction with unilateral PM. These findings were consistent with the pathology. The changes were more obvious in proton density-weighted images than in T2-weighted images, which thus differ from the changes in common gliosis. The other patient with the syndrome of PM and progressive ataxia did not show any olivary change. These changes on MRI are considered to indicate pseudo-hypertrophy of the inferior olives, although this is not consistently shown by the imaging method.