Emmanuel I. Skalidis

Myocardial perfusion in patients with permanent ventricular pacing and normal coronary arteries

OBJECTIVES The purposes of this study were to test the specificity of dipyridamole myocardial perfusion scintigraphy in patients with permanent ventricular pacing (PVP) and to evaluate coronary blood flow and reserve in these patients. BACKGROUND Permanent ventricular pacing is associated with exercise perfusion defects on myocardial scintigraphy in the absence of coronary artery disease (CAD). On the basis of studies in patients with left bundle brunch block, coronary vasodilation with dipyridamole has been proposed as an alternative to exercise testing for detecting CAD in paced patients, but this approach has never been tested. METHODS Fourteen patients with a PVP and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In these patients and in eight control subjects, coronary flow velocities were measured in the left anterior descending coronary artery (LAD) and in the dominant coronary artery before and after adenosine administration. RESULTS In the paced patients, coronary flow velocities in the LAD and in the dominant coronary artery were significantly lower than those in the control subjects. In addition, seven patients showed perfusion defects on dipyridamole thallium-201 single-photon emission computed tomography, with a specificity of 50% for this test. The defect-related artery in these patients had lower coronary flow reserve (2.6 +/- 0.5) as compared with those without perfusion defects (3.9 +/- 1.0, p < 0.05) or the control group (3.5 +/- 0.5, p < 0.05). CONCLUSIONS Permanent ventricular pacing is associated with alterations in regional myocardial perfusion. Furthermore, abnormalities of microvascular flow, as indicated by reduced coronary flow reserve in the defect-related artery, are at least partially responsible for the uncertain specificity of dipyridamole myocardial perfusion scintigraphy.

Phasic coronary flow pattern and flow reserve in patients with left bundle branch block and normal coronary arteries.

OBJECTIVES The purpose of this study was to determine whether scintigraphic myocardial perfusion defects in patients with left bundle branch block (LBBB) and normal coronary arteries are related to abnormalities in coronary flow velocity pattern and/or coronary flow reserve. BACKGROUND Septal or anteroseptal defects on exercise myocardial perfusion scintigraphy are common in patients with LBBB and normal coronary arteries. METHODS Thirteen patients (7 men, age 61+/-8 years) with LBBB and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In all patients and in 11 control subjects coronary blood flow parameters were calculated from Doppler measurements of flow velocity in the left anterior descending coronary artery (LAD) before and after adenosine administration. RESULTS The time to maximum peak diastolic flow velocity was significantly longer both for the seven patients with (134+/-19 ms) and for the six without (136+/-7 ms) exercise perfusion defects than for controls (105+/-12 ms, p < 0.05), whereas the acceleration was slower (170+/-54, 186+/-42 and 279+/-96 cm/s2, respectively, p < 0.05). Coronary flow reserve in the patients with exercise perfusion defects (2.7+/-0.3) was significantly lower than in those without (3.7+/-0.5, p < 0.05) or in the control group (3.4+/-0.5, p < 0.05). CONCLUSIONS Patients with LBBB have an impairment of early diastolic blood flow in the LAD due to an increase in early diastolic compressive resistance resulting from delayed ventricular relaxation. Furthermore, exercise scintigraphic perfusion defects in these patients are associated with a reduced coronary flow reserve, indicating abnormalities of microvascular function in the same vascular territory.

Absence of atherosclerotic lesions in the thoracic aorta indicates absence of significant coronary artery disease

Atherosclerotic lesions may be readily visualized in the thoracic aorta using transesophageal echocardiography. The absence of aortic plaque in the thoracic aorta rules out significant coronary artery obstruction whereas the existence of the former appears to be a sensitive and specific predictor of the latter.

AAIR Versus DDDR Pacing in Patients with Impaired Sinus Node Chronotropy: An Echocardiographic and Cardiopulmonary Study

The aim of this study was to compare AAIR and DDDR pacing at rest and during exercise. We studied 15 patients (10 men, age 65 ± 6 years) who had been paced for at least 3 months with activity sensor rate modulated dual chamber pacemakers. All had sick sinus syndrome (SSS) with impaired sinus node chronotropy. The patients underwent a resting echocardiographic evaluation of systolic and diastolic LV function at 60 beats/min during AAIR and DDDR pacing with an AV delay, which ensured complete ventricular activation capture. Cardiac output (CO) was also measured during pacing at 100 beats/min in both pacing modes. Subsequently, the oxygen consumption (VO2at) and VO2at pulse at the anaerobic threshold were measured during exercise in AAIR mode and in DDDR mode with an AV delay of 120 ms. The indices of diastolic function showed no significant differences between the two pacing modes, except for patients with a stimulus‐R interval > 220 ms, for whom the time velocity integral of LV filling and LV inflow time were significantly lower under AAI than under DDD pacing. At 60 beats/min, CO was higher under AAI than under DDD mode only when the stimulus‐R interval was below 220 ms. For stimulus‐R intervals longer than 220 ms, and also during pacing at 100 beats/min, the CO was higher in DDD mode. The stimulus‐R interval decreased in all patients during exercise. The time to anaerobic threshold, VO2at ond VO2at pulse showed no significant differences between the two pacing modes. Our results indicate that, at rest, although AAIR pacing does not improve diastolic function in patients with SSS, it maintains a higher CO than does DDDR pacing in cases where the stimulus‐R interval is not excessively prolonged. On exertion, the two pacing modes appear to be equally effective, at least in cases where the stimulus‐R interval decreases in AAIR mode.

Plasma Levels of Nitrites/Nitrates in Patients with Chronic Atrial Fibrillation are Increased after Electrical Restoration of Sinus Rhythm

AbstractIntroduction: Patients with persistent atrial fibrillation (AF) have hemodynamic changes, which impair endothelial cell function resulting in decreased nitric oxide (NO) production. The aim of this work was to assess endothelial function in AF patients before and at various time points after cardioversion. Methods: Forty-two patients with AF and 21 normal and age-adjusted healthy controls were studied. Nitrites and nitrates (NOx) and von Willebrand factor (vWf) concentrations were measured on blood samples taken just before cardioversion and over a 30 day period after the procedure. Results: Plasma levels of NOx in AF were significantly lower compared to healthy controls (p < 0.001), but after cardioversion gradually increased to approach to those of the healthy controls by the end of the first month of sustained sinus rhythm (p = 0.004). Interestingly plasma levels of NOx were negatively correlated to left atrial volume measured by ultrasonography (r = −0.34, p < 0.05). Plasma levels of vWf in AF patients were significantly higher compared to the healthy controls (p < 0.01) but with sustained sinus rhythm decreased (p = 0.02). Conclusion: The parallel normalization of the NOx titers and vWf levels suggests that vascular endothelial function improves after 30 days of normal sinus rhythm.

Phasic coronary blood flow velocity pattern and flow reserve in the atrium: regulation of left atrial myocardial perfusion.

OBJECTIVES The purpose of this study was to assess rest and stress atrial coronary blood flow (CBF) velocity and flow reserve. BACKGROUND Because of the limitations of the methods used until now for assessing myocardial perfusion (MP) in the small mass of atrial tissue, data are lacking for human atrial MP. METHODS Seventeen patients with suitable coronary anatomy underwent CBF velocity measurements with the use of a Doppler guide wire in the proximal left circumflex coronary artery (LCx) and left atrial circumflex branch (LACB), at baseline and after adenosine administration. All measurements were performed at resting heart rate and at 100 and 120 beats/min. RESULTS Coronary blood flow velocity in the LACB showed a predominant systolic pattern in contrast to the diastolic pattern of the LCx. There was a disproportionate increase in baseline time-averaged peak coronary flow velocity (cm/s) between the LACB and LCx during the two levels of pacing-induced stress (16.8 +/- 5.5 vs. 16.2 +/- 5.1 at rest; 22.9 +/- 7.9 vs. 18.4 +/- 5.2 at 100 beats/min; and 27.1 +/- 8.0 vs. 20.4 +/- 5.1 at 120 beats/min; significant interaction, p < 0.001), but there were no significant differences in coronary flow reserve (CFR). CONCLUSIONS Coronary blood flow in the left atrium is out of phase with that in the ventricular myocardium, showing a predominant systolic pattern. Although atrial and ventricular CFR show no significant differences at rest and with two levels of stress, the disproportionate increase in atrial blood flow velocity during stress indicates a peculiarity of atrial perfusion regulation.

Electrocardiographic appearance of old myocardial infarction in paced patients.

KOCHIADAKIS, G.E., et al.: Electrocardiographic Appearance of Old Myocardial Infarction in Paced Patients. This study evaluated the possibility of diagnosing chronic myocardial infarction in the presence of the pacing electrocardiogram. Forty‐five patients with known myocardial infarction (anterior 23, inferior 22) and 26 healthy controls were studied. After coronary angiography, pacing was applied from the right ventricular apex, and the sensitivity, specificity, and average diagnostic accuracy of five criteria on the paced electrocardiogram were assessed: (1) Notching 0.04 second in duration in the ascending limb of the S wave of leads V3, V4, or V5 (Cabreras sign); (2) Notching of the upstroke of the R wave in leads I, aVL, or V6 (Chapmans sign); (3) Q waves > 0.03 second in duration in leads I, aVL, or V6; (4) Notching of the first 0.04 second of the QRS complex in leads II, III, and aVF; (5) Q wave > 0.03 second in duration in leads II, III, and aVF. The most sensitive criteria, for anterior and inferior myocardial infarctions were Cabreras and Chapmans (91.1 and 86.6%, respectively). All criteria had low specificity (range 42.3–69.2%). The combination of Cabreras and Chapmans sign decreased the sensitivity to 77.7%, but increased specificity to 82.2%. The sensitivity and specificity of all the criteria were independent of the myocardial infarction site. In paced patients, the application of electrocardiographic criteria, and especially the combination of Cabrera and Chapman, provides useful clinical information in recognizing prior myocardial infarction but not in assigning the specific infarct site.

Oxidative stress changes after stent implantation: A randomized comparative study of sirolimus-eluting and bare metal stents

BACKGROUND Although oxidative stress plays an important role in the pathophysiology of restenosis, its role following the implantation of sirolimus-eluting stents (SES) is unknown. METHODS We examined the relation between total peroxides (TP), a marker of oxidative stress, and in-stent late luminal loss over a 6-month follow-up in patients with stable coronary artery disease and compared the results from SES with those from bare metal stents (BMS). We enrolled 75 consecutive patients, who underwent successful PCI and were randomly allocated to SES (n=37) or BMS (n=38). Blood samples were taken 24 h before, at 24 h, 48 h and 1 month after angioplasty; levels of TP were determined on each occasion. Follow-up coronary angiography was performed 6-8 months later. RESULTS TP levels in the BMS group were significantly higher at 24 h and 48 h compared to baseline (p=0.006 for both). At one month there was a significant decline from the 48 h levels (p=0.029) to levels slightly, but not significantly higher than baseline. In contrast, in SES TP levels showed no significant changes during the first 48 h, while they declined to levels somewhat lower than baseline at 30 days. A significant correlation was found between TP changes and in-stent late luminal loss at 6 months in both groups. CONCLUSION Our study showed that patients with stable coronary artery disease who received SES have a different behavior of oxidative stress after stenting compared with BMS, and this could contribute to the difference in restenosis rate between these 2 types of stents.

Electrocardiographic Diagnosis of Acute Myocardial Infarction in the Presence of Ventricular Paced Rhythm

KOCHIADAKIS, G.E., et al.: Electrocardiographic Diagnosis of Acute Myocardial Infarction in the Presence of Ventricular Paced Rhythm. ST‐segment deviation was recently described as the only ECG finding that was useful in the diagnosis of acute myocardial infarction during right ventricular pacing. This report shows that the same sign may also indicate the amount of myocardium in jeopardy and the coronary artery responsible.

Vascular endothelial growth factor protein levels and gene expression in peripheral monocytes after stenting: a randomized comparative study of sirolimus: eluting and bare metal stents.

AIMS Although previous studies have indicated that vascular endothelial growth factor (VEGF) plays an important role in the vascular-healing process after stent implantation, its effect on in-stent restenosis is unclear. We assessed VEGF serum protein levels and gene expression in peripheral monocytes in relation to in-stent restenosis after implantation of sirolimus-eluting (SES) and bare metal stents (BMS) in a non-blinded, randomized study. METHODS AND RESULTS Forty-two patients (28 men, age 62 +/- 11 years) with stable angina, who underwent elective single-vessel percutaneous coronary intervention, were randomized to SES (n = 21) or BMS (n = 21) implantation. VEGF protein levels in the BMS group showed an increasing trend (P = 0.083), whereas in the SES group they decreased significantly (P = 0.002). BMS induced up-regulation of VEGF mRNA levels, whereas for SES down-regulation was observed. There was no correlation between serum levels and late luminal loss. A significant correlation was found between VEGF gene expression and late luminal loss in both groups (BMS: r = 0.98, P < 0.001; SES: r = 0.65, P = 0.002). CONCLUSION SES, in comparison with BMS, results in lower VEGF protein levels and gene expression in peripheral monocytes. The latter shows a positive relationship with in-stent late-luminal loss, suggesting an essential role in the reduced in-stent restenosis seen in SES.