The survey was designed as a joint initiative of the HFA and the EHRA.14 The design of the CRT-Survey II and the detailed content of the electronic case report form (eCRF) have been previously published.14

Each participating country was represented by a national coordinator appointed by the president of the corresponding national society of cardiology. The national coordinator was responsible for obtaining approval from the ethics committee if needed, recruiting the participating centers, and distributing information from the scientific committee to all participants. In the case of Spain, 54 hospitals were invited to participate, of which 36 actively participated in the survey and included at least 1 patient.

The study included any patient selected for implantation with a CRT pacemaker (CRT-P) or CRT defibrillator (CRT-D) in any of the 36 participating Spanish hospitals. Patients were included regardless of procedural success. We included primary implants and upgrading procedures from a previous pacemaker or a previous implantable cardioverter-defibrillator. We excluded generator replacement and surgical revisions of previously implanted devices because the survey was designed to include only the implantation of new CRT devices.

The patient inclusion period was initially planned to last 9 months. The first patient was included on October 1, 2015. Subsequently, the scientific committee decided to extend the inclusion period by 6 months to December 31, 2016, with the aim of increasing the size of the sample in order to increase its representativeness and thus enable comparisons between the participating countries.

Each of the participating centers completed a questionnaire on its characteristics, such as the size of the hospital (number of beds), the type of center (public/private/university), the catchment population, the operator's degree of specialization, infrastructures, and the routine CRT device implantation protocol used.14

The participating centers were asked to include patients who were scheduled to receive a CRT device and to complete an electronic case report form (eCRF) for each patient. The eCRF collected information on patient characteristics, complementary tests performed, indication for CRT, implant procedure, and a short-term follow-up that included adverse events and complications until hospital discharge.14 No data were recorded on longer-term follow-up. The anonymity of the participating patients was ensured at all times. The study protocol was approved by the Clinical Trials Committee of the Hospital Universitari i Politècnic La Fe de Valencia.

The eCRF, data processing, and statistical analyses were conducted by the Institut für Herzinfarktforschung.15 The daily operational control of the progress of the survey was conducted at Stavanger University Hospital, University of Bergen, Norway.

Continuous variables are expressed as medians [interquartile range]. Discrete variables are expressed as percentages. Data obtained by the Spanish centers and the participating centers were compared using the Student t test for continuous variables and the chi square test for discrete variables. A P value of ≤ .05 was used as a cutoff for statistical significance.

The median number of annual CRT implants reported by the 36 Spanish centers was 30 [21-50], which was significantly less than the median of 55 [33-100] reported by the other participating countries (P < .001) (Table 3). Most of the participating Spanish centers were university hospitals (94.3%), whereas in the other countries there was broad representation of nonuniversity teaching hospitals (25.9%) and private hospitals (8.8%).

In Spain, the median age of the study patients was 69 [62-75] years, which was similar to the other patients (70 [62-76] years) (Table 4). There was a lower percentage of patients aged 75 years or more in Spanish centers (27.9%) than in the other centers (32.4%; P=.007). There was a very similar percentage of implants in men and women: 75% and 25% in Spanish centers, respectively, and 75.8% and 24.2% in the other centers, respectively. The percentage of implants conducted via scheduled admission was lower in Spain than in the other countries (68.8% vs 77.6%; P < .001). However, the number of patients included in clinical trials was higher in Spain (11.0% vs 8.1%; P=.003). The type of heart disease underlying the need for implantation significantly differed between Spain and the other countries, with a lower percentage of patients with ischemic dilated cardiomyopathy (38% vs 45%), and a higher percentage of patients with nonischemic dilated cardiomyopathy (NICM) (53.1% vs 49.5%) or with other etiologies of heart failure (8.9% vs 5.4%; P < .001).

In addition, a smaller percentage of patients had a history of atrial fibrillation (34.9% vs 41.3%; P < .001) and valvular disease (21.4% vs 27.7%; P < .001) (Table 4). However, other comorbidities, such as chronic obstructive pulmonary disease, diabetes mellitus, anemia, and kidney disease were more common in the patients included in the Spanish centers. In total, 26.1% of all implants were upgrading procedures in patients who already had a device.

Most patients were in New York Heart Association (NYHA) functional class II (46.9%) or III (47.5%) (Table 5). In contrast to the other countries, a greater percentage of Spanish patients were in class II (46.9% vs 36.9%; P < .001), whereas the percentage of Spanish patients in class IV was negligible (0.7% vs 4.8%; P < .001).

At the time of implantation, 72.6% of the Spanish patients were in sinus rhythm; the percentage of Spanish patients with atrial fibrillation was slightly lower than that of patients in the other countries, although without reaching statistical significance (23.1% vs 25.9%; P=.078). Mean QRS duration was 159 ± 24ms. In total, 73% of Spanish patients had a QRS equal to or greater than 150ms and 19.3% had a QRS of 130ms to 150ms. These values are similar to those of the other countries. There was a greater percentage of complete left bundle branch block (LBBB) (81.7% vs 72%; P < .001) and complete right bundle branch block (RBBB) (8.9% vs 6.4%; P=.005) (Table 5) in Spanish patients than in the other patients.

In total, 23.3% of the Spanish patients had a left ventricular ejection fraction (LVEF) greater than or equal to 35%, and 33% had at least moderate mitral regurgitation. The most frequent indication for CRT implantation was heart failure and wide QRS (55% of patients). In total, 55% of patients had heart failure, severe left ventricular (LV) dysfunction, and indication for implantable cardioverter-defibrillator. In 24.8% of patients, the only reason for implantation was the need for stimulation and a predicted high percentage of stimulation.

In Spain, the implant success rate was 95.9% (Table 6). In contrast to the other countries, implants were mainly performed by electrophysiologists (92.9% vs 75.7%; P < .001). The number of unsuccessful implants was significantly higher in Spain (4.1% vs 2.6%; P=.009). In total, the percentages of Spanish patients with CRT-D (68.8%) and CRT-P (31.2%) were similar to those of the other countries. More CRT-Ds than CRT-Ps (80.1% vs 19.9%) were implanted in patients with ischemic dilated cardiomyopathy than in patients with NICM (64.7% and 35.3% respectively; P < .001). A higher percentage of CRT-Ps than CRT-Ds (58.5% vs 41.5%) were implanted in patients whose indication was the need for stimulation or a predicted high percentage of stimulation. In Spain, the median duration of the implantation procedure was significantly higher than the mean (120 [90-150] minutes vs 90 [65-120] minutes; P < .001). In total, 11.4% of LV leads were surgically implanted in the epicardium. Multipolar LV leads were used in 74.2% of patients; this percentage was much higher than that registered in the other countries. The LV lead was in lateral segment locations in 86.7% of patients and in medial segment locations in 72.9% of patients. The periprocedural complication rate was 7.2%, which was significantly higher than the mean of 5.4% reported by the other participating countries (P=.028) (Table 7).

Median hospital stay was significantly lower in Spain than in the other countries: 2 [2-7] vs 3 [2-7] days (P < .001) (Table 8). The major adverse event rate during hospitalization was 3.5%, including a mortality rate of 0.4%. Before hospital discharge, AV and VV intervals were reprogrammed using device-specific software in 35% of patients. In 98% of patients, postimplant follow-up was performed in the same implantation center. In total, 55.8% of the patients were followed up by remote monitoring; this percentage was significantly higher than that in the other countries (27.7%; P < .001).

This study is limited by its use of a survey format, which only collects pre-established data from the time of implantation to the time of hospital discharge. Therefore, the validity of the data on complications and morbidity and mortality may be limited by their being underestimated due to the lack of patient follow-up. In addition, only 20.1% of the total number of predicted CRT implants were collected by the survey during the inclusion period and therefore the data obtained may not reflect the current situation in Spain. More extensive surveys could be conducted to confirm these findings.