Reliability of Transesophageal Pacing in the Assessment of Sinus Node Function in Patients with Sick Sinus Syndrome

The purpose of this study was to find out whether transesophageal pacing could be utilized for assessment of sinus node function in patients with sick sinus syndrome (SSS). In 17 patients with SSS (study group) we compared the results of sinus node tests obtained both in the basal state and after pharmacological autonomic blockade by endocavitary stimulation and, 24 hours later, by transesophageal pacing. In another group of 17 patients with SSS (control group), we compared the results obtained by two endocavitary studies. In "study group", sinus cycle length (SCL) and corrected sinus node recovery time (CSRT) did not show significant differences between the two studies both in the basal state and after autonomic blockade, whereas sinoatrial conduction time (SACT) was more prolonged during esophageal pacing (P less than 0.01). In "control group", sinus node measures did not show significant differences between the two studies. In the "study group," the following coefficients of correlation were obtained in the basal state; SCL, r = 0.65, CSRT, r = 0.57, SACT, r = 0.52 and after autonomic blockade: SCL, r = 0.95, CSRT, r = 0.62 and SACT, r = 0.53. In the basal state, the correlation for SCL and CSRT between the two studies was lower in the "study group" than in the "control group" (P less than 0.05), whereas after autonomic blockade the correlation for sinus node measures did not show significant differences between the two groups of patients. These data suggest that transesophageal study influences the autonomic tone regulating the sinus node; however, it is not responsible for important variations in sinus node measures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atrial and Ventricular Pressures in Atrial Flutter

The hemodynamic effects of atrial flutter (AF) are unknown. The purpose of the present study was to investigate the changes in atrial and ventricular pressures after induction of AF. In 23 patients with paroxysmal AF (age 59 ± 9 years), a hemodynamic study was performed both during sinus rhythm and after induction of the tachyarrhythmia. During AF, 13 patients showed a fixed 2:1 AV conduction and 10 patients showed variable conduction. Mean right and left atrial pressures increased (P < 0.001) and right and left ventricular end-diastolic pressures decreased (P < 0.001) after induction of AF. Roth the increase in mean atrial pressures and the decrease in ventricular end-diastolic pressures were present either in the patients with fixed 2:1 AV (heart rate: 133 ± 15 beats/min) or in those with variable conduction (heart rate 96 ± 15 beats/min), but were more marked in the former. AF produces an impairment of atrial function, as evidenced by the increase in mean atrial pressures and reduction in ventricular end-diastolic pressures in the absence of an elevated heart rate. The mechanisms responsible for the increase in mean atrial pressures are unknown; however, atrial contractions against closed AV valves seem to play an important role.     

A Case of Atrial Tachycardia Treated with Ivabradine as Bridge to Ablation

Ivabradine is indicated in cardiac failure and ischemia to reduce sinus rate by inhibition of the pacemaker I(f) current in sinoatrial node. We report a case of an 18‐year‐old woman with left atrial tachyarrhythmia resistant to several antiarrhythmic drugs and to electric cardioversion who responded only to ivabradine, which significantly reduced heart rate without abolishing the arrhythmia itself. An ectopic focus in the ostium of left pulmonary veins was found and the patient was successfully ablated. We suggest that ivabradine might be therefore useful in the treatment of supraventricular tachyarrhythmias due to an enhanced automaticity.     

Different Trends of Changes in Heart Rate Variability in Patients with Anterior and Inferior Acute Myocardial Infarction

Modifications in heart rate variability (HRV) parameters occur after acute myocardial infarction. The aim of this study was to evaluate the trend of HRV change during the acute phase and the first month after myocardial infarction, and establish whether they were affected by the anterior or inferior location of the infarction. The time-domain HRV measures of 59 patients with a first uncomplicated acute myocardial infarction were computed from 24-hour ECG recordings made on days 1, 2, 10, and 28 after hospital admission. At day 1, the mean RR cycle length (NN), the standard deviation of the NN intervals (SDNN), and the root mean square successive difference of NN intervals (RMSSD) were lower in the patients with anterior myocardial infarction. Although the parameters were similar in all of the patients at day 28, their behavior over time was different (P = 0.01): the SDNN in the patients with inferior myocardial infarction had decreased to the values found in anterior myocardial infarction patients by day 2 but, at day 10, both NN and SDNN tended to recover in both groups; RMSSD had diminished in both groups by day 2, but at day 10, had increased in the patients with anterior, but not in those with inferior myocardial infarction. These findings suggest that (1) in the very early phase of myocardial infarction, HRV is different in the two locations, (2) during the first hours of myocardial infarction patients with inferior location showed a greater vagal activity than patients with anterior location that became lower at day 10, and (3) the recovery of HRV is an early phenomenon in both groups, being already evident by the second week after myocardial infarction.     

Duplex-Doppler assessment of cirrhosis in patients with chronic compensated liver disease

Portal venous flow velocity (PFV) was measured with duplex-Doppler equipment in 50 normal subjects and in 117 patients with suspected chronic liver disease who showed no evidence of decompensation such as ascites, hepatic encephalopathy, jaundice or oesophageal bleeding. All the patients underwent percutaneous liver biopsy which demonstrated non-cirrhotic liver disease in 58 cases (CH-patients: steatosis 8, persistent chronic hepatitis 8, active chronic hepatitis 42) and liver cirrhosis in the other 59 cases (LC-patients). The normal subjects and the CH-patients had similar values of max-PFV and mean-PFV (max-PFV 26.7±3.2 and 25.7±3.4 cm/s respectively; mean-PFV 22.9±2.8 and 22.4±3.8 cm/s respectively). The LC-patients’ values (max-PFV 19.3±3.5; mean-PFV 16.9±2.9) were significantly lower than those of the normal subjects (P<0.001) and of the CH-patients (P<0.001). Considering the normal max-PFV to be in the range 20–33.1 cm/s (mean±2 s.d. of the normal subjects, 95% confidence limits), max-PFV was reduced in 0/50 normal subjects, 1/58 CH-patients and 39/59 LC-patients (66.1% sensitivity; 98.2% specificity). In conclusion, the duplex-Doppler measurement of PFV is of great interest in the diagnostic study of patients with suspected chronic compensated liver disease and in the early diagnosis of cirrhosis. A low max-PFV is a reliable pointer to liver cirrhosis, whereas a normal max-PFV indicates a non-cirrhotic liver disease but is less probative. Each centre should standardize normal PFV values in order to establish their own threshold value for diagnosing liver cirrhosis.     

Linear and cyclic synthetic peptides related to the main autophosphorylation site of the Src tyrosine kinases as substrates and inhibitors of Lyn †

Tyrosine protein kinases (TPKs) of the src family contain two major phosphoacceptor sites which are homologous to the Tyr 416 and Tyr 527 of pp60^c-src. The former represents the main autophosphorylation sites of these enzymes, and its phosphorylation correlates with increased kinase activity. It has previously been demonstrated that the Src-like tyrosine kinase expressed by the oncogene lyn displays a high affinity toward the heptapeptide H-Glu-Asp-Asn-Glu-Tyr-Thr-Ala-OH, which reproduces the main autophosphorylation site of the Src family enzymes [Donella-Deana, A., Marin, O., Brunati, A.M. & Pinna, L.A. (1992) Eur. J. Biochem. 204 , 1159–1163]. Our study was addressed to the synthesis of some derivatives of this sequence in order to obtain both peptide substrates suitable for the detection of the Src-like tyrosine kinase activity and active site-directed inhibitors specific for this class of enzymes. For this purpose we synthesized by classical solution methods the heptapeptide and its dimeric form. Moreover, in order to improve the proteolytic resistance of these peptides we also synthesized their cyclic derivatives and their N-terminal acetylated and C-terminal amidated analogs. The correlation between the different structural properties induced by the modifications of the native sequence and the propensity of the peptides to act as Lyn substrates was examined. The kinetic data obtained indicate that the extent of the peptide phosphorylation varies considerably depending on the flexibility and length of the analogs. While the cyclization and the C-terminal amidation of the heptapeptide are detrimental for the Lyn activity, dimeric derivatives display very favourable kinetic constants. In particular the cyclic dimer is an especially suitable substrate for the tyrosine kinase and a powerful inhibitor of both the phosphorylation activity of Lyn and the enzyme autophosphorylation. © Munksgaard 1995.