Clinical significance of N-terminal-probrain natriuretic peptide in hypertrophic cardiomyopathy

Identifying Cardiac Diseases using Cardiac Biomarkers in Rhesus Macaques (Macaca mulatta)

Cardiac biomarkers are an important tool for diagnosing cardiac diseases in both human and veterinary patients. Serum concentrations of N-terminal probrain natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) have been used to indicate the presence of various cardiac diseases including hypertrophic cardiomyopathy (HCM) in various species including humans. However, these cardiac biomarkers have not been established as a diagnostic tool for detecting cardiac disease in rhesus macaques. In the rhesus macaque colony at the California National Primate Research Center, naturally occurring HCM and various other cardiac diseases have been identified. In this study, commercially available assays were used to measure serum cTnI and NT-proBNP concentrations to evaluate their utility as a diagnostic screening tool for cardiac diseases in rhesus macaques. This study revealed that the serum cTnI concentration was significantly higher in animals with echocardiographically apparent cardiac disease as compared with the animals that had no cardiac structural and functional changes (the control group). However, no significant differences were detected between animals with HCM and non-HCM cardiac disease. Because the area under the receiver operating characteristic curve was 0.81 when the serum cTnI was compared between the control and cardiac disease groups, serum cTnI was considered a moderately accurate test to predict the presence of cardiac disease. The optimal cut-off value of serum cTnI concentration for diagnosis of cardiac disease was 0.0085 ng/mL, with a sensitivity of 0.68 and specificity of 0.94. Significant but weak correlations were noted between the serum cTnI concentration and several echocardiographic parameters. Conversely, no significant differences in NT-proBNP concentrations were detected between animals with and without cardiac diseases. In conclusion, measurement of serum cTnI can be used to aid in diagnosing cardiac diseases in rhesus macaques. However, cTnI measurement does not replace echocardiographic evaluation to diagnose cardiac diseases in rhesus macaques due to the poor sensitivity of the assay and the weak correlation to with more established echocardiographic markers for cardiac disease.

Orthostatic blood pressure test for risk stratification in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death (SCD) in young adults, mainly ascribed to ventricular tachycardia (VT). Assuming that VT is the major cause of (pre-) syncope in HCM patients, its occurrence is essential for SCD risk stratification and primarily preventive ICD-implantation. However, evidence of VT during syncope is often missing. As the differentiation of potential lethal causes for syncope such as VT from more harmless reasons is crucial, HCM patients were screened for orthostatic dysregulation by using a simple orthostatic blood pressure test.

METHODS

Over 15 months (IQR [9;20]) 100 HCM patients (55.8±16.2 yrs, 61% male) were evaluated for (pre-)syncope and VT (24h-ECGs, device-memories) within the last five years. Eighty patients underwent an orthostatic blood pressure test. Logistic regression models were used for statistical analysis.

RESULTS

In older patients (>40 yrs) a positive orthostatic test result increased the chance of (pre-) syncope by a factor of 63 (95%-CI [8.8; 447.9], p<0.001; 93% sensitivity, 95%-CI [76; 99]; 74% specificity, 95%-CI [58; 86]). No correlation with VT was shown. A prolonged QTc interval also increased the chance of (pre-) syncope by a factor of 6.6 (95%-CI [2.0; 21.7]; p=0.002).

CONCLUSIONS

The orthostatic blood pressure test is highly valuable for evaluation of syncope and presyncope especially in older HCM patients, suggesting that orthostatic syncope might be more relevant than previously assumed. Considering the high complication rates due to ICD therapies, this test may provide useful information for the evaluation of syncope in individual risk stratification and may help to prevent unnecessary device implantations, especially in older HCM patients.

Utility of measuring plasma N-terminal pro-brain natriuretic peptide in detecting hypertrophic cardiomyopathy and differentiating grades of severity in cats

BACKGROUND

Cats with hypertrophic cardiomyopathy (HCM) often have no clinical signs or subtle signs. Measurement of N-terminal pro-brain natriuretic peptide (NT-proBNP) has been demonstrated in people to be highly specific for heart disease and also correlates with severity of HCM. NT-proBNP may also be valuable in detecting and grading HCM in cats, but results to date have been equivocal.

OBJECTIVES

The aims of this study were to evaluate NT-proBNP as a screening test for diagnosis of HCM in cats and determine an appropriate cut-off value and to determine if NT-proBNP concentrations correlated with severity of HCM in cats.

METHODS

Plasma NT-proBNP concentrations were measured in 201 cats using an ELISA designed for use in cats. Cats were classified using echocardiography as clinically healthy controls (n=99) or cats with equivocal (n=9), mild (n=15), moderate (n=17), or severe (n=61) HCM.

RESULTS

NT-proBNP concentrations (median; 25th-75th interquartile percentiles) in mildly (216.1; 87.6-392.5 pmol/L), moderately (282.7; 131.9-466.6 pmol/L), and severely (839.5; 655.3-1046.4 pmol/L) affected cats were significantly higher than those in healthy controls (18.9; 3.4-62.4 pmol/L). Concentrations in severely affected cats were significantly higher than in cats from other HCM groups. There was no significant difference between mild and moderate HCM. Cut-off values >49 pmol/L had a sensitivity of 97.8% and specificity of 66.7%; >100 pmol/L had a sensitivity of 92.4% and specificity of 93.9%; and >150 pmol/L had a sensitivity of 88% and a specificity of 100%.

CONCLUSIONS

NT-proBNP with a cut-off value of >100 pmol/L was useful in detecting even mild HCM. Cats with increased NT-proBNP concentrations should be examined by echocardiography.

NT-proBNP measurement fails to reliably identify subclinical hypertrophic cardiomyopathy in Maine Coon cats

The purpose of this study was to evaluate the value of measuring plasma NT-proBNP concentration as a screening tool in cats with varying severity of subclinical hypertrophic cardiomyopathy (HCM). Plasma NT-proBNP concentration was measured in 35 cats that had previously been classified as normal, equivocal, moderate HCM or severe HCM via echocardiography. No cat had ever been in congestive heart failure. Cats with severe HCM had a significantly higher NT-proBNP concentration compared to the other groups (P<0.0003), however, the sensitivity of NT-proBNP for diagnosing cats with severe disease was only 44% (cutoff≤100pmol/l) to 55% (cutoff≤40pmol/l). There was no significant difference in NT-proBNP concentration between normal, equivocal and moderate categories (sensitivity for detecting moderate HCM was 0%). Based on the results of this study, NT-proBNP concentration is not considered adequate as a screening test for detecting mild to moderate HCM in Maine Coon cats and it appears that it may miss many cats with severe HCM.

Investigation into the use of plasma NT-proBNP concentration to screen for feline hypertrophic cardiomyopathy

OBJECTIVE

To evaluate the utility of feline NT-proBNP plasma concentration [NT-proBNP] as a screening tool for cats with subclinical hypertrophic cardiomyopathy (HCM).

ANIMALS, MATERIALS AND METHODS

Forty adult Maine Coon or Maine Coon crossbred cats from the feline HCM research colony at the University of California, Davis were studied. All cats had previously been genotyped as heterozygous or negative for the A31P myosin binding protein C (MYBPC) mutation. Echocardiograms were performed to assess the severity of HCM in each cat. Blood samples were collected for evaluation of [NT-proBNP].

RESULTS

In these cats with severe HCM, [NT-proBNP] was significantly elevated (P<0.0001) when compared to all other groups of cats and an [NT-proBNP]>44pmol/L accurately predicted the presence of severe HCM. However, [NT-proBNP] was not increased in cats with moderate or equivocal HCM when compared to normal cats. Cats heterozygous for the MYBPC mutation had a significantly elevated [NT-proBNP] when compared to cats without the A31P mutation (P=0.028).

CONCLUSIONS

Measurement of [NT-proBNP] has a high sensitivity and specificity as a means of detecting severe HCM in cats, but it is not sensitive for the identification of moderate HCM as judged by the evaluation of Maine Coon and Maine Coon cross cats in our colony. Consequently, we conclude that this test cannot be used to screen cats for the presence of mild to moderate HCM.

A new technique to avoid the intraoperative complications of septal myectomy in patients with obstructive hypertrophic cardiomyopathy

Although transaortic septal myectomy in obstructive hypertrophic cardiomyopathy (OHC) is accepted as a safe procedure, it may end up with serious peroperative complications. We developed a practical method to avoid this unfavorable outcome by using a 20-cc syringe body. We believe this apparatus will provide safe and effective septal myectomy procedures without additional cost.