Maria Cristina Tentori

Automatic beat-to-beat left heart AV normalization: Is it possible?

Programming the right heart AV interval to a normal value may cause a nonphysiological left heart AV due to interatrial and interventricular conduction delays, thus affecting cardiac performance. Since AV normalization at rest and exercise may be invalidated by pacing or sensing (mode) changes, the aim of this study was to (1) study the feasibility of a mode independent pacemaker (PM) algorithm for automatic beat‐to‐beat left AV normalization, (2) establish normal values for the time between mitral flow A wave (Af) and ventricular activation (Va), the AfVa interval, the mechanical surrogate of left AV, and (C) determine the range of values of the interatrial electromechanical delays (IAEMDs) and the effect of RA pacing. To pace with the proper right AV, the previously reported RV‐paced interventricular electromechanical delay and the interatrial electromechanical delay, either P‐sensed (IAEMDs) or atrial‐paced (IAEMDp) are required inputs. Data were collected during diagnostic echo Doppler studies in 84 subjects divided in three groups: (1) control with narrow QRS and no structural heart disease (n = 33, age 50 ± 21 years, 42% men); (2) patients in sinus rhythm with diverse cardiac pathologies except LBBB (n = 39, age 69 ± 14 years, 56% men), and (3) DDD‐paced patients (n = 12, mean age 71 ± 6 years). Normal values of AfVa were established from the control group, while IAEMDs and IAEMDp and active atrial flow time (A‐peak), in all subjects. The algorithm was tested by computer simulation under all possible modes with the following calculation: RAV = N + IAEMD − IVD, where RAV is the right AV, N is the desired normal AfVa value, IAEMD is either P‐sensed or A‐paced, and IVD is close to zero for intrinsic narrow QRS and biventricular pacing, or 79 ms for RV pacing. The results demonstrated (1) Normal (controls) AfVa: 85 ± 15 ms (range 52–110 ms); (2) IAEMDs (All): 84 ± 16 ms; (3) atrial pacing prolonged IAEMDs by 57 ± 18 ms (from 93 ± 15 to 150 ± 25 ms, P < 0.0001); and (4) Computer simulation of rate and mode changes validated the normalization algorithm. An automatic, beat‐to‐beat left AV normalization algorithm to preserve a normal AfVa without a hemodynamic sensor is feasible. The normal value of AfVa is 85 ± 15 ms. (PACE 2003; 26:2103–2110)

Frequency‐Domain Analysis of Heart Rate Variability During Positive and Negative Head‐Up Tilt Test: Importance of Age

The study of autonomic behavior during a head‐up tilt test (HUT) has been deemed important to understand the loss of consciousness mechanism. Though HRV in patients with HUT(+) and HUT(‐) has been compared, few trials emphasized the importance of age. HRV in fre‐quency domain was analyzed based on 5‐minute samples in the supine position, and between 5 and 10 minutes during early tilt test (R1) in 102 patients with one or more episodes of syncope (mean age 44.3 ± 20.8, range 15‐85 years, 55 women). Two subgroups were selected afterwards: (1) young patients between 15 and 35 years of age (41 patients) and (2) elderly patients aged 60 or more (36 patients). The following parameters were taken into account: the sum of low (LF) and high frequency (HF) (LF and HF in absolute values and in normalized units), the LF/HF ratio (L/H ratio), and the percentage of change between base line and Hi values. The HRV behavior in young and elderly patients with positive and negative HUT was established. We then analyzed the correlation between HRV and age and HUT outcome. A multiple re gression analysis encompassing age, HUT outcome, gender, and number of syncope episodes was per formed. In young patients, the LF and HF areas and the L/H ratio changed significantly between baseline and Rl. The L/H ratio increases from baseline to Rl. Conversely, these differences were not significant in the elderly. No differences between HUT(+) and HUT(‐) within the same age group were observed. Age related significantly to practically ail HRV parameters analyzed, whereas the tilt test outcome correlates poorly with HF normalized units and LF normalized units during Rl, and the L/H ratio changes between baseline and Rl. By means of a multivariate analysis, only age shows a significant correlation with the HRV values. Despite an all age triggering of vasovagal syncope during HUT, the young and elderly pa tients’autonomic behavior differs. The young considerably increase their sympathovagal balance during HUT, whereas the elderly have a mitigated autonomic response. No significant differences were observed during the first minutes of the test between those with a HUT(+) and those with a HUT(‐) within the same age group. Age, and not the HUT response, is the major determinant of the autonomic behavior during early HUT.

Insulin sensitivity in young women with vasovagal syncope.

BACKGROUND Insulin, in addition to its known metabolic effects, has sympatho-excitatory and vasodilatory actions on muscular blood vessels. The goal of this study was to evaluate insulin sensitivity in young women with vasovagal syncope and positive tilt test results (HUT+) and to compare it with that in patients with negative tilt test results (HUT-) and in control subjects without a history of syncope. METHODS Different indices of insulin sensitivity were obtained by an oral glucose tolerance test (OGTT) in 13 young women with syncope and HUT+ (age 26.8 +/- 9.1 years, body mass index 20.4 +/- 2.1), 8 patients with HUT- (age 26 +/- 5.6 years, body mass index 21.9 +/- 2.4), and 13 control subjects without syncope and HUT- (age 28.9 +/- 8.8 years, body mass index 23.1 +/- 1.7). The following parameters were assessed: fasting glucose and insulin levels (G(0), I(0)); G(0)/I(0) ratio; G(0) x I(0); areas under the curve for glucose and insulin; homeostatic model assessment (HOMA); quantitative insulin sensitivity check index (QUICKI); and composite whole-body insulin sensitivity index (ISI). RESULTS G(0) and I(0) values were significantly lower in patients with HUT+ than in control subjects (G(0) 4.9 vs 81.9, P <.05, I(0) 4.7 vs 9.1, P <.005). All the fasting values-based indices (ie, HOMA 0.9 vs 1.9, P <.005) and the ISI (12.8 vs 7.1, P =.01) differed significantly in both groups. None of the parameters showed significant differences between patients with HUT- and control subjects. Sixty-one percent of patients with HUT+ had a vasovagal reaction during OGTT. CONCLUSIONS Young women with vasovagal syncope and HUT+ have a greater insulin sensitivity. They have a propensity to reproduce symptoms during the OGTT. This hypersensitivity could be one of the predisposing factors for vasovagal episodes.

Role of nitric oxide in young patients with vasovagal syncope

AIMS Nitric oxide (NO) formed in the vascular endothelium produces, among other effects, a strong vasodilation. In order to evaluate the possible role of NO in hypotension induced by head-up tilt test (HUT), we measured plasma levels of its metabolites, nitrites and nitrates (NOx), during the test. METHODS AND RESULTS Twelve patients with vasovagal syncope and positive HUT [HUT(+)] (mean age: 23+/-5 years) and 13 healthy volunteers with negative HUT (controls) (mean age: 24+/-5 years) were included. Venous blood samples were obtained during the baseline stage for biochemical measurements. Plasma values of NOx were obtained under baseline conditions (T0), at the end of the HUT (T1), and 15 min after the end of the HUT (T2). The baseline biochemical values as well as haemodynamic parameters were similar in HUT(+) patients and controls. NOx plasma values (in micromol/L) were as follows [HUT(+) vs. controls]: T0: 5.7+/-1.6 vs. 8.8+/-4.7 (P=0.05), T1: 6.1+/-3.2 vs. 8.5+/-3.6 (P=NS), and T2: 6.1+/-3 vs. 10.2+/-8.9 (P=NS). The NOx levels were directly correlated with the insulin levels (Spearmans R=0.53, P=0.008). CONCLUSION Baseline plasma levels of NOx were significantly lower in HUT(+) patients than in controls. However, since the expected increase in NOx values during HUT-induced syncope was not observed, the possible role of NO in vasovagal hypotension is uncertain.

Frozen Leads: A Simple Solution for an Old Problem

Entrapment of pacemaker leads in the pacemaker header, or “frozen leads,” is an old problem with a difficult answer that can only be resolved during a pulse generator (PG) replacement procedure. Lead damage during removal of the frozen lead from the PG header, especially on pacemaker dependent patients, has always been a major concern, for excessive traction on the lead may cause damage to either or both the insulation and conductor. There are several reports in the literature describing this problem, but the suggestion of Ramicone et al. to use a drill to rapidly release the lead seemed to be a feasible approach. Therefore, it is the aim of this article to present the authors’ experience of the use of an electric drill to remove frozen leads from PG headers. During the past 17 months, 113 leads were disconnected from 72 pacemakers at the Hospital Juan A. Fernández (Table I). These procedures consisted of PG replacements, upgrades, or lead extractions. The mean implant duration of those leads was 57 months (range 1–188 months). Forty were atrial leads, and 72 were ventricular leads (Table II). Nine (12.5%) bipolar ventricular leads were entrapped at the connector. The mean implant duration of all frozen leads was 73 months (range 14–126 months). Two of these leads were damaged while traction was applied to disconnect the lead from the header, requiring implantation of new leads. Subsequently, the electric drill method was applied. A 3,500 rpm drill with double isolation, fitted with a 2-mm drill bit was used. No current leakage could be measured between exposed metal parts (including the drill bit) and the ground, active pole or neutral of the 220 V alternating current (AC) power outlet. In the last two cases the drill bit was fitted with an insulating material (polyamide 6) at the point of contact with the drill chuck (Fig. 1). The closed end of the epoxy header was perforated (Fig. 2), in alignment with the end of the pin receptacle (Fig. 3). Once the perforation reached the lead pin, a gentle pressure with the nonrotating drill bit was sufficient to push the lead out of the header. Seven leads were salvaged by this simple approach. The salvaged leads had a mean implant time of 64 months. Seven of the nine pacemakers with frozen leads were made by Intermedics Inc. (Angleton, TX, USA) (Table III); all of them with bipolar sidelock fixation, and the frozen leads were always ventricular. Of the 72 pacemakers, 12 were made by Intermedics. Seven of the 11 PGs (Intermedics) with side-lock fixation had entrapment problems (63.6%).

Lack of current implantable cardioverter defibrillator guidelines application for primary prevention of sudden cardiac death in Latin American patients with heart failure: a cross-sectional study.

AIMS This cross-sectional study evaluated the application of accepted international implantable cardioverter defibrillator (ICD) guidelines for primary prevention of sudden cardiac death in patients with heart failure. METHODS AND RESULTS The PLASMA (Probabilidad de Sufrir Muerte Arritmica) study was designed to characterize management of cardiac patients in Latin America. Twelve centres included 1958 consecutively admitted patients in cardiology units in 2008 and 2009. Discharged patients were evaluated for primary prevention, ICD indication and prescription by general cardiologists. Of 1711 discharged patients, 1525 (89%) had data available for evaluating indication status. Class I indications for ICD therapy were met for 153 (10%) patients based on collected data. Only 20 (13%, 95% confidence interval: 7.7-18.4%) patients with indication were prescribed an ICD. Patients prescribed an ICD were younger than patients who were not prescribed an ICD (62 vs. 68 years, P < 0.01). The reasons given by cardiologists for not prescribing an ICD for 133 patients with an indication were: indication criteria not met (75%), life expectancy <1 year (9.7%), rejection by the patient (5.2%), no medical coverage paying for the device (3.7%), psychiatric patient (2.2%), and other reasons (4.2%). CONCLUSIONS In Latin America, international guidelines for primary prevention ICD implantation are not well followed. The main reason is that cardiologists believe that patients do not meet indication criteria, even though study data confirm that criteria are met. This poses a significant challenge and underlines the importance of continuous and improved medical education.

Unusual placement of a pacemaker pocket.

Because of infection and extensive radiation injury to the skin of the chest wall, a dual chamber pacemaker was implanted deep to the clavicle. The wound has been stable and comfortable for 1 year and pacemaker programming has been unimpaired.

Breast cancer and pacemakers

AIMS The combination of breast cancer and the need for a pacemaker is infrequent, and device implantation under these circumstances may be a technical challenge with several treatment options, most of them complex. METHODS AND RESULTS Eight patients, all women, with an average age of 69.62 ± 11.4 years. We present a technique for patients with bilateral breast cancer who need a pacemaker or those who had already implanted a device and developed a homolateral breast cancer. All the pacemakers were implanted in a neck pocket, as a first implantation or if they were moved from a prepectoral pocket to the neck. Seven patients had a good outcome and one had an infection. CONCLUSION We suggest a simple alternative to lead extraction or epicardial approach in patients with coexisting breast cancer and the need for a rhythm control device consisting in placing the device in a neck pocket and preserving the existing leads by tunnelling them either above or below the clavicle.

Symptomatic, Inspiration-Induced Atrioventricular Block: Treated with Pacemaker Implant: SYMPTOMATIC, INSPIRATION-INDUCED ATRIOVENTRICULAR BLOCK

The respiratory sinus arrhythmia is the most common cardiac arrhythmia. It consists of phasic variations of sinus cycle length produced by an autonomic reflex, and is characterized by increased heart rate during inspiration and decline in expiration. This phenomenon is due to a reduction of the parasympathetic tone during inspiration, causing a rise in the heart rate, while during expiration the opposite phenomenon occurs. This arrhythmia is more frequent in young adults, although it can also be seen in any age group.

885 The bradycardia-hypotension reaction during head-up tilt test: clinical and hemodynamic characteristics related to blood pressure and heart rate behavior during the early stage of the test

There was no correlation between delayed increase of aldosterone and NTG provocation during HUT. The delayed increase of aldosterone observed in 22% of all patients was related to syncope recurrence during follow-up, but not to the phase of tilt in which syncope occurred. Conclusions: 1. The delayed increase of aldosterone concentration during HUT-induced syncope is a risk factor of syncope recurrence during follow-up. 2. The delayed increase of aldosterone could be the marker of disturbed activation of RAA system predisposing the patients to vasovagal syncope.