Geographic and Segment Information | Note 16. Geographic and Segment Information We identify operating segments based on the way we manage, evaluate and internally report our business activities for purposes of allocating resources and assessing performance. We have two reportable segments: Cardiac Surgery and Neuromodulation. The Cardiac Surgery segment generates its revenue from the development, production and sale of cardiovascular surgery products. Cardiac Surgery products include oxygenators, heart-lung machines, autotransfusion systems, mechanical heart valves and tissue heart valves. The Neuromodulation segment generates its revenue from the design, development and marketing of neuromodulation therapy for the treatment of drug-resistant epilepsy and treatment resistant depression. Neuromodulation products include the VNS Therapy System, which consists of an implantable pulse generator, a lead that connects the generator to the vagus nerve, surgical equipment to assist with the implant procedure, equipment to enable the treating physician to set the pulse generator stimulation parameters for the patient, instruction manuals and magnets to suspend or induce stimulation manually. On January 16, 2018, we acquired the remaining 86% outstanding interests in ImThera which is also included in our Neuromodulation segment. ImThera manufactures an implantable device for the treatment of obstructive sleep apnea that stimulates multiple tongue muscles via the hypoglossal nerve, which opens the airway while a patient is sleeping. “Other” includes corporate shared service expenses for finance, legal, human resources and information technology and corporate business development (“New Ventures”). New Ventures is focused on new growth platforms and identification of other opportunities for expansion. During the three months ended March 31, 2018 , we began to include the results of heart failure within the Neuromodulation segment for internal reporting purposes in order to manage and evaluate business activities for purposes of allocating resources and assessing performance. Previously, the results of heart failure were reported within Other. Segment results for the three months ended March 31, 2017 have been restated to conform to the current period presentation. Net sales of our reportable segments include revenues from the sale of products they each develop and manufacture or distribute. We define segment income as operating income before merger and integration, restructuring and amortization of intangibles. We operate under three geographic regions: United States, Europe, and Rest of world. The table below presents net sales by operating segment and geographic region (in thousands): Three Months Ended March 31, 2018 2017 Cardiopulmonary United States $ 38,445 $ 32,176 Europe 36,870 30,609 Rest of world 49,815 44,513 125,130 107,298 Heart Valves United States 6,536 6,069 Europe 12,116 10,347 Rest of world 12,390 15,490 31,042 31,906 Cardiac Surgery United States 44,981 38,245 Europe 48,986 40,956 Rest of world 62,205 60,003 156,172 139,204 Neuromodulation United States 77,992 73,659 Europe 10,291 7,929 Rest of world 5,561 5,571 93,844 87,159 Other 382 462 Totals United States 122,973 111,904 Europe (1) (2) 59,277 48,885 Rest of world 68,148 66,036 Total (3) $ 250,398 $ 226,825 (1) Net sales to external customers includes $8.2 million and $6.8 million in the United Kingdom, our country of domicile, for the three months ended March 31, 2018 and March 31, 2017 , respectively. (2) Europe sales include those countries in which we have a direct sales presence, whereas European countries in which we sell through distributors are included in Rest of world. (3) No single customer represented over 10% of our consolidated net sales and no country’s net sales exceeded 10% of our consolidated sales except for the U.S. Operating income by segment is as follows (in thousands): Three Months Ended March 31, Operating Income from Continuing Operations 2018 2017 Cardiac Surgery $ 10,258 $ 16,033 Neuromodulation 38,734 40,756 Other (22,820 ) (16,866 ) Total reportable segment income from continuing operations 26,172 39,923 Merger and integration expenses 2,960 2,186 Restructuring expenses 1,881 10,030 Amortization of intangibles 8,801 7,960 Operating income from continuing operations $ 12,530 $ 19,747 Assets by reportable segment (in thousands): Assets March 31, 2018 December 31, 2017 Cardiac Surgery $ 1,386,282 $ 1,386,032 Neuromodulation 715,611 532,894 Other 345,843 334,276 Discontinued operations 257,140 250,689 Total assets $ 2,704,876 $ 2,503,891 Capital expenditures by segment (in thousands): Three Months Ended March 31, Capital expenditures 2018 2017 Cardiac Surgery $ 3,131 $ 3,794 Neuromodulation 347 1,461 Other 1,443 1,203 Discontinued operations 925 1,658 Total $ 5,846 $ 8,116 The changes in the carrying amount of goodwill by reportable segment for the three months ended March 31, 2018 were as follows (in thousands): Neuromodulation Cardiac Surgery Other Total December 31, 2017 $ 315,943 $ 425,882 $ 42,417 $ 784,242 Goodwill as a result of acquisition (1) 87,063 — — 87,063 Foreign currency adjustments — 4,259 — 4,259 March 31, 2018 $ 403,006 $ 430,141 $ 42,417 $ 875,564 (1) Goodwill recognized as a result of the ImThera acquisition. Refer to “ Note 3. Business Combinations .” Property, plant and equipment, net by geography are as follows (in thousands): PP&E March 31, 2018 December 31, 2017 United States $ 60,684 $ 62,154 Europe 119,630 119,133 Rest of world 11,387 11,072 Total $ 191,701 $ 192,359 |